Fallout 4 exploits

Ahab's helm glitch
This requires you to have the Automatron add-on, a robot workbench, and the Sentry Ahab's helm looted from Ahab. It will not work with an "Ahab's Helm" created using the robot workbech.
 * 1) Create a new automatron.
 * 2) In the "Head" slot, build the "Sentry Head".
 * 3) In the "Head Armor" slot, build any mod other than "No Head Armor" or "Ahab's Helm". Either of the "Reaper Helm" or "Hydraulic Frame" makes this easier, since they appear directly above and below "Ahab's Helm".
 * 4) Ensure you have none of the components required to build "Ahab's Helm", either in your workshop or in your inventory, and that you're carrying the Sentry Ahab's helm looted from Ahab in your inventory.
 * 5) Now in the "Head Armor" slot, when you try to attach the "Ahab's Helm" mod, instead of attaching the one you're holding, it will instead create a new one, without using any materials, and grant you the XP for crafting it.
 * 6) Now re-attach the other previously created "Head Armor" mod, and a duplicated "Ahab's Helm" with a different base ID will be added to your inventory.
 * 7) Repeat from step 5. Each iteration will grant you some XP and another duplicated "Ahab's Helm", which can be sold for caps later.

General advice and notes
This is not an exploit, but rather taking advantage of reoccurring radiant quests. Several quest givers accessible at lower levels such as Preston Garvey at Sanctuary Hills, or Knight Rhys and Scribe Haylen at the Cambridge Police Station, offer an unlimited number of quests to Radiant locations that should respawn when a new quest is started. Repeating Quartermastery or Cleansing the Commonwealth for the Brotherhood of Steel will provide a steady supply of XP from killing enemies and completing quests, as well as loot and ammunition from respawning Radiant locations.

Armor mods
You can use mods from lower tier armor for higher tier of the same type, such as crafting a deep-pocketed mod for standard combat armor and applying it on heavy combat armor without having the perk to craft it for Heavy. (This goes for all armor types with "standard", "sturdy" and "heavy" versions - raider, metal, leather, combat - and is likely by design, rather than an exploit per se.)

Free Fat Man/mini nukes
You can easily gain an infinite amount of free Fat mans and mini nukes. All you have to do is: (If you plan on selling the Fat Mans, do so before you leave Goodneighbor, as she will restock caps every week.)
 * 1) Go to Kill or Be Killed (KLEO's shop) in Goodneighbor. To KL-E-0's left, there will be a Mini-Nuke. To her right, there should be a Fat Man.
 * 2) Put your cursor over the Fat Man/mini nuke.
 * 3) Hold down the activation button so that you are holding the Fat Man. (Do not tap the button, or you will just steal it)
 * 4) Walk into the upstairs portion of the shop and go to the right side of the room.
 * 5) Enter sneak mode. The game may say caution, in which case, you may have to move around a little bit until the game says that you are hidden.
 * 6) Tap A/X to drop the Fat Man/mini nuke, then steal it.
 * 7) Fast Travel away and wait a week.
 * 8) Repeat.

V.A.T.S. Auto-aim without using AP
Like in Fallout 3, picking a target in V.A.T.S. auto-aims the crosshair reticule to that target. This can still be exploited to high degree in close quarters situations (mole rat rush) by:


 * 1) Going into V.A.T.S. and highlighting the target or part you want to hit.
 * 2) Cancel out of V.A.T.S. and repeatedly press the fire button as you do so.
 * 3) Hold the V.A.T.S. button again to quickly slow down time again and select another target.
 * 4) Repeat.

This is applicable in long-range engagements, but practicality varies. In close quarters, it is more consistent.

Free ammunition exploit
This allows for you to have a full magazine of ammo which does not take away from your current supply.


 * 1) Select the weapon you wish to have a free magazine for.
 * 2) Find any container, and store all ammunition for that weapon in the container.
 * 3) When the free ammo is exhausted, go back to the container and pick up your ammo for that gun.
 * 4) (if planning to re-apply) unequip and re-equip the weapon, and repeat.

While this exploit is under effect, you can not reload your weapon and swapping to any other weapon or picking up ammo for the glitched weapon will automatically void the exploit.

Duplicate materials
This allows for infinite raw materials at any settlement Note this is best with no junk in the workbench.

If done correctly you should have had the scrap menu pop up and go away and be at the store menu. You should check and now have cloned resources. This is most effective with large quantities and can also be used as a caps glitch. Just trying to be helpful, I find it works better if, after you release the scrap button just quickly press and hold the accept and store buttons at the same time. You should have both menues open for as long as you hold the buttons, the just release the select button, it should scrap and still have the option to store. let go of the scrap button and press the accept button.
 * 1) drop desired materials on the ground
 * 2) press the "scrap" button (Xbox X, PS4 square)
 * 3) press the "accept" button in almost rapid succession (Xbox A, PS4 X)
 * 4) press the "store"(Xbox B, PS4 circle) button in almost directly after "accept"

''Note: The "scrap" and "accept" actions trigger on button release, whereas the "store" action triggers on button press. Since you essentially want to trigger the "store" action while the "scrap" and "accept" actions are queued, the simplest way to do this is to hold (but don't release) "scrap" and "accept" with the fingers of one hand, and ready one finger of your other hand over the "store" button. Then, release "scrap" and "accept" in quick succession (remember, it's the releasing of these buttons that triggers these actions - and they need to be released in the correct order) while simultaneously tapping "store" with your other hand. Using this technique should make it significantly easier to pull off this trick consistently.

The simple, more consistent way to do this resource duplicate process, and also makes it possible to be sure you do not destroy the item you are trying to get resources from is as follows:

Drop item on the ground Go into workshop mode the same as above Hover over item Press and hold "scrap" (square on ps4) button with one finger. Here is the tricky part, with another finger or hand, you need to press "store" (circle on ps4) and hold it, at nearly the exact time you release square.

While holding circle now you should notice that both accept menus are there. If you get them both go ahead and press accept on them both while still holding square. This will scrap the item, and return the original copy of it to storage.

If you only get one menu or the other you can just cancel it without destroying the item or having to go take it back out of the workshop bench.

Duplicate weapons
This allows for duplication of any weapon.
 * 1) Kill an enemy wielding the desired weapon, such that the weapon falls to the ground.
 * 2) Instruct your follower to pick up the weapon, and then aim your crosshairs at the corpse and get the hovering list of their inventory.
 * 3) When the follower picks up the weapon, it does not disappear from the hovering list, allowing you to also loot it from the corpse and resulting in both you and your follower now having duplicate copies of the weapon.

Physics engine glitches

 * Sometimes V.A.T.S. will end and seem like the target was missed, but then a few seconds later, the bullet hits. This was tested multiple times at point blank and ranged V.A.T.S. The target can be used as a meat shield while the bullet is "frozen"
 * On occasion, Dogmeat will sit as if in his doghouse and spin in place. While this is occurring, no movement commands work, i.e. "Go" then point to a location, "Sit Doghouse", etc. The solution is to start traveling any direction so he runs in front to lead the way. It may reoccur if you then stop moving. Rebooting the PS4 from a full (non-sleep) power-down may solve this or it may go away on its own.
 * You can walk backwards up any wall in the game by dropping an item, crouching down, grabbing it without putting it in your inventory (hold X on PS4), standing up, and walking backwards towards a wall. Works best with flat walls and walls that don't have a lip at the top as you might end up falling once you reach the lip. Fall damage still applies while doing this. Use power armor.
 * With the 1.0 build, it is possible to fly by grabbing an item you are standing on. This may kill the player though.

Money & experience

 * The game allows saving during npc dialogs which makes it easy to reload the game and retry any option which may influence caps, experience, etc. outcome when talking.

Succeed on every risky dialog choice
To achieve a 100% success rate on dialog choices:

This is a useful way to bypass the dialog choice mini game.
 * 1) Go into the dialog menu (you may already be there).
 * 2) Press start and quicksave.
 * 3) Attempt dialog choice.
 * 4) If it fails, reload save until successful.
 * 5) It appears you have an infinite amount of attempts when you would normally have one.

Trigger bright idea on quest completion
Idiot savant on second rank gives you 5* XP on random actions, including quest completions (basic go fetch quests 200XP+). Quicksave trick also works with this:
 * 1) Quicksave before handing quest in
 * 2) Reload quicksave until you trigger perk. May take a few attempts, but easily worth it to gain 5 quests worth of XP.

Infinite XP

 * After reaching the Prydwen and completing Show No Mercy, speak to Proctor Teagan (Weapons Merchant). Ask him about extra work and he will give you a mission acquiring crops from the citizens of the Commonwealth. The first location will be a random settlement (Tenpines Bluff, Somerville Place, and the Slog confirmed) and, after completion, will award around 100 caps and 125 XP (leveled, above level 50 rewards 390XP). Asking for extra work again will give you the exact same quest as before, convincing the same settlement to contribute crops. Repeat for unlimited XP and Caps.
 * After reaching the Brotherhood of Steel's Prydwen, you can go up to Proctor Quinlan and ask to do a scribe escort. After he gives you the quest, you can head out to the flight deck (where you can see an area near a couple of barrels) and you can kill the scribe in secrecy. Once this is done, you can return back to him saying the scribe died, and he will award you with XP and caps still.
 * Alternatively, instead of sniping the scribe from the flight deck, you can choose to fast travel down to the airport, sprint to him, and speak with him as to get him to follow you. In this manner, you can "beam him up" back to the Prydwen by once again fast traveling back to it. Now, take the scribe to an area where you can execute him while hidden (best done by going into the Quarters at the end of the hall, just behind you when you enter the main hall). Executing the scribe in person will net you 3-5 stimpaks and a holding of fusion cells, usually 16. Make sure you're not seen and kill the scribe quickly (easily done by temporarily setting the game at very easy and stealth killing him.) You can then turn right around and speak with Proctor Quinlan just down the hall. Rinse and repeat for a healthy supply of stimpaks and fusion cells to go with your XP and caps.
 * You will receive the same amount of caps and XP whether you complete the mission as normal or simply kill the scribe.

Notes This is best accomplished with Black-Rim Glasses (CHR +1), Gray Knit Cap (LCK +1), and Reginald's Suit (CHR +3). (Or any other CHR and LCK awarding apparel).


 * Termination of the residents will result in termination of the exploit.
 * Though the XP may stop being granted for the exploit, you will still receive the caps. It can be fixed by attempting the mission and the scribe being killed by an enemy.

Repeatable lockpicking
If you happen to find a locked safe right next to a terminal that can also control the lock on the safe, it is possible to pick the lock, use the terminal to lock the safe, then repeat the same process over and over. You will earn the XP for picking the lock every time you do it. This is most useful with a master lock, and even faster with the unbreakable lockpicks perk. This method cannot however be used to infinitely gain approval with Piper. (It can by quicksaving and reloading in between each try)
 * One location with such a safe is Cambridge Polymer Labs near a desk in the upper floor of the lab.
 * Another location is in the Security office to the left of the main entrance in the Super-Duper Mart in Lexington. NOTE: at level 7, it is only an advanced lock (please confirm)
 * Expert Safe next to an Advanced Terminal in the radioactive shack at Jalbert Brothers Disposal.
 * Expert Safe next to a Novice Terminal on the roof of Weston water treatment plant.
 * Novice Safe next to a Novice Terminal inside the Leasing Office of Fiddler's Green Trailer Estates.
 * Inside main building in University Point (Unknown if level based). Requires expert lockpicking skill for one door to get to terminal and safe.
 * Expert safe inside tall blue building immediately north of Faneuil Hall.
 * Safe to the left of Lance's terminal in West Everett Estates.
 * Safe on the opposite wall from a terminal inside the Suffolk County charter school.

Effect exploits
Bleeding effects stack and do not extend. Meaning high ROF bleed weapons do increased damage.

Non-player character-specific exploits

 * Dogmeat is able to fetch a variety of items:
 * The Cryolator which normally requires Master lock picking
 * Items that are out of reach like the Grenade Bouquet hung over the entrance to West Everett Estates
 * It is possible to have up to three companions. By meeting X6-88 to hunt the rogue, then simply not going to the targets location, he will follow you anywhere you go. However, he will fight with BoS and other various allies. Travis Miles, the radio DJ, can become a follower the same way, giving you three companions. To change their gear, drop weapons or armor and have them walk over it. If it's better than what they already have, they will sometimes pick it up and equip it.
 * This also works with Preston in Taking Independence; he will follow you indefinitely as long as you don't destroy enough eggs to spawn the mirelurk queen.


 * All companions (except Dogmeat) are able to pick up an infinite amount of items even when their carrying capacity is maxed out. You simply drop the item you want them to carry and then command your companion to pick the item up. They will pick the item up and put it in their inventory regardless of the weight they are already carrying.
 * This does not let the companion carry more items through "Trade".
 * Some Companions will refuse to pick up items that are marked as stolen so they must be added through "Trade" or carried yourself.

Companion character and settler clothing glitch/exploit
Companions and settlers can be reduced to wearing only underwear, even though the game UI tries to prevent it by hiding their currently worn piece of clothing from their inventory. (This doesn't work on Danse or Nick, who won't change their clothes at all.)
 * This WILL work with Nick if you have him enter power armor. His trench coat will appear in his inventory. Rather than wearing underwear, he will have the normal synth unclothed appearance.

Trade with a companion/settler. Give them a piece of over-clothing, a single piece that takes up armor slots such as a dress for the legs and torso or Radstag Outfit, and then press Y/Triangle/T to have them equip it. Their previous clothing is now listed in their inventory. Now give them a piece of armor that can't be worn over the clothing and press Y/Triangle/T to equip. This removes the clothing. Then un-equip the armor and they have nothing on.

Settler weapon exploit
If you give a settler any weapon and provide one ammo for the given weapon, the settler has infinite ammo for their equipped weapons. This is particularly useful for the Minigun.

Jamaica Plain
There are 49 steel, crystal, and fiber optics if all of the laser trip wires just prior to the room with the two Protectrons are disarmed, in the town hall basement. If you hit the red button at the end corridor you can start the trip wires over and can get an infinite amount of steel, crystal and fiber optics. This can be done even after destroying all turrets. A small amount of XP will be awarded for each as well.

Gameplay exploits
In Saugus Ironworks, mini-boss Slag tells Jake to kill the prisoner. If you successfully convince Jake to not harm the prisoner, Slag will wait for a few seconds before turning hostile. If you Save during this brief moment, then when you reload from that save, all the baddies will remain friendly until you fire at them. This affords you the opportunity to lay numerous mines at all of the enemies feet, which do not explode as long as they remain friendly. Then take a shot at one of them, they will all turn hostile, and all of the mines will blow, killing them all very easily. This exploit has only been tested at Saugus Ironworks, but may work in other similar situations if enemies wait for a while before turning hostile and you are able to save during that countdown.

Sentry Tower
An exploit used in order to keep an impossible to breach defense. Build a high stairway above your base and place several sentries. Then scrap all wood and the sentries will stay afloat, whenever the base is attacked the sentries will have a 360° view of the base.

Traps
The exploit is used by intentionally detonating/ tripping them then if you reload the traps will be pre-tripped/detonated (bottle caps from bottle cap mines are not there)

Changing building limit without console

 * 1.Drop weapons from inventory
 * 2.Enter building mode
 * 3."store" those dropped weapons to workbench from building mode (pc button TAB/ Xbox One B button/ PS4 Circle button). Scrapping the weapon will also work in reducing the size if done from building mode.


 * NOTE: This also seems to work with junk items. The method tested was simply to:
 * 1. Drop all junk items on the floor.
 * 2. Enter building mode.
 * 3. Scrap items to increase building limits.
 * NOTE: This exploit has been re-tested on PS4 (14th Apr 2016) after 1.5 patch, and it is still working.

Free shield
Using the hold mechanic, you can hold an item and use it as a shield. This does not prevent you from using your weapon, making it an effective tool. First, drop an item (preferably on with a large surface area) on the ground. Now, hold the grab button (a on Xbox One and x on PS4) until you are holding the item. You now have a shield that bullets can not pass through. Notes:
 * Be wary of your weight limit, as picking up something already on the ground may make you over encumbered.
 * This best works with items such as: Power armor, Fat Man or minigun.
 * Different weapons shoot at different heights (differences can be also be caused by whether you're using Hip-fire or Aiming). Due to this, you won't be able to use some weapons.

Re-Speccing (PC)
This is not so much of an exploit as a method to change your build while staying somewhat honest. While this is still not included in the game, you do not gain any kind of unfair advantage except the hindsight.
 * 1. Determine the ID for the perk you no longer want.
 * 2. In console use player.removeperk perkID command
 * 3. Still in console use CGF "Game.AddPerkPoints" Integer to add the number of perk points equivalent to the number of perks you just removed.
 * 4. Add the new perks, either in console or normally through Pip-Boy interface.

PS4 only exploits
==Robot workbench exploit == This glitch unlocks/creates MODS without having the necessary components for or perk level for. all you do is hold down a direction until it speed scrolls and immediately hit X on the one right after the locked mod while still scrolling (note you do have to be able to create/Istall the mod right next to it) it might take a couple tries but when you hit X on the one you were aiming for it will always highlight the one right before the one you hit X on. This trick works works both up an down as long as there is enough room for it to start speed scrolling. It can get a little tricky when the mod you want is near the end of the list. WARNING you might want to take off any mod you want to keep that it is replacing because it will turn into whatever mod your installing (this may also work on XBOXbut has not been tested)

Patched exploits
The following exploits were patched in the versions specified below. If you find that any other exploits, that worked in a previous version, no longer work after a patch, please move them here.

On consoles, it's possible to delete and reinstall the game to revert the game version back to v1.1.21 if you want to reproduce these. You may need to disconnect the console from the internet to prevent it from auto-updating to the latest version. It is unlikely that you will be able to load save files created with later versions of the game, so this will only work if you intend to start a new character. Saves created in v1.1.21 should load fine if you then update the game back to the latest version.

Patch 1.2
The following exploits no longer work as of patch 1.2:-
 * The infinite caps exploit, i.e. glitching ammo from vendors for infinite selling caps.
 * Crafting exploit for infinite experience on Xbox One. Still works on PS4 until patch 1.4

Patch 1.3
The following exploits no longer work as of patch 1.3:-

Dogmeat duplication

 * 1) Drop item
 * 2) Command Dogmeat
 * 3) Have "Dogmeat pick up xxx" (Best if he's a distance from the item)
 * 4) While he's moving towards item, adjust position so reticule changes for you to "Pick up xxxx"
 * 5) When he approaches, Dogmeat will stop and dip his head to pick up item. JUST as he starts dipping his head, pick up the item. You'll hear the "picked up" sound and Dogment will appear to have nothing in his mouth. He'll come to you and drop the duped item.
 * This works with bullets or any stacked item. After Dogmeat drops the duplicated item, one bullet/one item from the stack, drop the rest of your duplicated item inside your inventory on to the ground. Quick save then manually quit to the main menu reload the quick save and voila you now have two copies of the stacked item.
 * For PC players, it only works on low FPS count (24-30 FPS is ideal for this)
 * As for magazines, will work with You're SPECIAL! only, allowing the character to max out his/her stats. After picking up a duplicated item, drop all issues and upon picking them up, you'll get the Choose Stat window.
 * With a base installation of the game on Xbox (without the Day 1 Patch) it has been reported that the player will be able to increase their S.P.E.C.I.A.L. to values above 10 using You're SPECIAL!
 * Also works well for duplicating vendor shipment papers for materials such as Adhesive or Aluminum
 * Armor however is near impossible to duplicate this way because he simply grabs near the beginning of his animation giving you little chance to grab it before he does

Unlimited Items and XP after patch
To obtain unlimited items (any item), you must have Dogmeat as a companion. For this instance, use copper. First go to a settlement of your choice, and begin the duplication process with Dogmeat. Once Dogmeat has picked up and dropped the copper, drop the copper you picked up. You should now have two different bars on the ground in front of you; one that says the amount you had in your inventory, and the single bar that Dogmeat picked up. At this point save the game. Full save or quick save, it doesn’t matter. You then need to quit the game and reenter the game through continue, or load your most recent save. Once done, two bars with the original amount are on the ground. Pick up first the item Dogmeat dropped and then the original item. Once this is done, drop both again, go into workshop mode and scrap both items. After this is complete, when you go into your workbench, take out the item just duplicated and drop it. It will be consolidated into one item. Rinse and repeat until you reach your desired amount.

(Update-March 2016) With the above exploit, you don't have to quit the game after saving. After dogmeat drops the junk item then you drop yours, save the game then go into build mode and scrap the items. This also works with stacked junk items. Was tested multiple times on PS4 using base game, no patches.

Once you have duplicated the copper to your desired amount, you will be able to build statues to increase your XP. (Picket Fences issue #3 magazine found in Saugus Ironworks)

Alternative Method (Junk items only): For this example, you have twenty copper in your Junk inventory. You drop it, use Dogmeat to duplicate it. Drop all the copper in your Junk inventory after dogmeat has dropped his. You should see twenty copper on the original bar and twenty on Dogmeat's duplicate bar. (If you dropped your copper from your inventory before Dogmeat does your copper bar and his may be reduced to one). At this point the above instructs to quick save, quit and load. You can actually scrap both in the workshop menu and it will show both as twenty and twenty as being scrapped. You should now have forty copper in your Workshop. You can extract the forty copper and rinse and repeat.

Note: Not only does this method save time, but also ensures that the junk items are joined together and do not separate when dropped. If you have less than six items the game will not ask to drop all together, so just use Dogmeat to make more than six and then follow the above guide.

Notes
 * You can only consolidate raw materials within your “Junk” tab. You can duplicate ammo this way, but you won’t be able to merge the ammo together.
 * Picking up items of 25k or more may cause the game to freeze, causing you to have to restart the console.

Weapon mod duplication
Buy a weapon modification from a vendor, such as "Triple barrel X+" and have an "accelerated barrel" for the minigun, and attach triple barrel X+ then switch to accelerated barrel. Now constantly between the two barrels and you should be awarded a triple barrel or triple barrel x+ every time you switch.

Patch 1.4
The following exploits no longer work as of patch 1.4:-

Crafting exploit for infinite experience
Every time the player crafts an item at a settlement, they earn experience, and the experience earned seems to depend on the overall value of consumed items used to craft the item. There is a method that can be used to create an infinite amount of crafting materials by purchasing one of the "shipment of xxx" dockets from a vendor. Therefore, any items crafted from said infinite material will yield the player an infinite amount of experience as long as they continue to farm the material, build an item crafted from the material, scrap all the items used to build the material (since you can only place so many items in a settlement) and repeat.

First, the player must obtain a "shipment of xxx" docket from a vendor, of which types are available vary from vendor to vendor. For the purposes of this small guide, which I will explain as to the reasons why in the next section, I suggest the player use the shipment of copper docket from Arturo in Diamond City. They simply need to purchase one, however it is most efficient if the player was to use the wait feature to purchase as many dockets as the player is willing to collect. Once obtained, the player should take the docket to one of their settlements. This is a very important note: DO NOT PLACE THE SHIPPING DOCKET INTO THE WORKSHOPS INVENTORY UNTIL YOU ARE READY TO PERFORM THE EXPLOIT. If you do, the docket(s) will (almost) immediately be converted into its shipped material and the docket(s) will disappear, requiring you to load an old save or buy a new one. It is highly suggested that, for this reason, the player saves the game quite frequently every time they go to access their workshops inventory. The next thing they should do is make sure there is no inventory in the workshop, and that the only junk item in your inventory is/are the docket(s). The next step is tricky, and it is advised that one saves before attempting it, and throughout save in tiers as to prevent you having to start all over: while in the workshops inventory, you are to press y (or triangle on the PS4 version) (to store all junk items) and IMMEDIATELY afterwards, press x (or square in the PS4 version) (to take all). If done properly and quickly enough, the materials provided from the docket should be created, and your player will collect the "shipment of xxx" docket without it disappearing. This method can be repeated quite quickly in succession, simply by rapidly pressing yxx (triangle, square, square, if played on the PS4 version) over and over again to store all junk, immediately collect all junk items in the workshop, and then open the workshops inventory again. Doing this obviously benefits the player in a multitude of ways: they can use this to farm an infinite amount of a rare/valuable crafting material (such as aluminum, copper, or adhesive) collect an infinite amount of caps from vendors simply by selling the farmed materials, or farming a vary large amount of experience points in a fairly short period of time by simply crafting something which uses this duplicated material over and over again.

It seems one of the best methods, if not the absolute best method, is to obtain the Picket Fences #3: Essential Upgrades! magazine from Saugus Ironworks, as this allows for the crafting of copper statues. The very first statue, which features a baseball player, uses 10 copper and provides the player character anywhere between 25-35 experience (based on the player's intelligence) every time it is placed. By walking backwards and rapidly pressing A (X in the PS4 version), the statues will be placed one after the next, netting the player several thousand experience points in just a few minutes. Exact gain of experience is difficult to determine, however trial of this exploit resulted in leveling up from level 35 to 100 within approximately 3 hours of gameplay.

EDIT: With extensive testing of this exploit, one was able to level up from level 1 at the very start of the game to level 271 (wherein all perks had been maxed out) in less than 18 hours of gameplay. While 18 hours of doing one action seems arduous, it is significantly more efficient than leveling up by playing the game normally, which one can estimate to be around 300+ hours of gameplay, even with high modifiers to Intelligence throughout.

Another Method, albeit slower, is to get specific Items and get to a Chem Workshop there you can for example craft Buffjet by pressing X and O on Playsation (A and B on Xbox) at the same time. If done correctly, the Crafting confirmation screen will appear, however it will be back at the crafting menu. If not done corrctly it will still be on the same page as before. This is also very easy to do as Buffout and Jet can be obtained in the beginning of the Game. Be reminded however that it will take longer.

Patch 1.5
The following exploits no longer work as of patch 1.5:-

Bypass approval cooldown timer
The Approval cooldown (e.g. the time you need to wait after crafting a mod for Codsworth / Preston or picking a lock for Piper until they "like" it again) can be reset by saving and reloading the game.

This works exceptionally well with MacCready, who will gain affinity points regardless of what you steal. With just the items available in the Third Rail where you recruit him, you can get the Long Road Ahead quest before leaving the building. You can gain approval by stealing, quicksaving, reloading, and stealing another item (vase, desk fan, etc).

Hacking robots with weapon
If you have a weapon equipped and see a robot (doesn't matter if its idle or actively attacking) you can zoom in using the weapon and hack that robot from a pretty far distance.