Experimental MIRV

The  is a unique Fat Man launcher that can be found in the bomb shelter area in the National Guard Depot on a table near the remains of the skeletons of the Keller Family, who play a central role during the player's acquisition of this weapon. This weapon is clearly and without a doubt the strongest weapon in the game, though excessively so.

Obtaining
The player must complete the unmarked quest Keller Family Refuge before they can gain access to the secure section of the depot housing the weapon.

However, if you crouch by the terminal and the bunker door, go into 3rd person, and rotate the cursor above the characters head and find the "Electrical switch button". This is not hard and works perfectly after about a minute. It's small but easy to find.

Tips

 * When fired, this weapon causes massive damage in the form of eight Mini Nukes. A random shotgun spread seems to be the path they take, usually 6 or 7 in a semi-tight group and one off in the distance. If aimed correctly, this weapon will kill anything in one hit, even Super Mutant Behemoths.
 * It will only fire eight Mini Nukes at once, no more, no less.
 * You'll have to learn how to measure the distance and height of the mini nukes' flight if you plan to use this, trying to use it like the Fat Man usually ends with a flash as a nuke hits the ground in front of you.
 * For the above reason, it is recommended that you should always use the Experimental MIRV in V.A.T.S . You should not fire or at least be cautious when firing up a hill or towards someone with obstacles in the way. Saving before firing is a good tip, as it is a waste of 8 mini-nukes if you miss. Mini nukes are difficult to find and are very expensive in the game, running at around 300 caps for one mini nuke.
 * The MIRV looks identical to the Fat Man, which means that it really should only be able to fire one mini nuke at a time, but somehow 7 more appear from the weapon all at the same time.

Background
MIRV is a military term for Multiple Independent Reentry Vehicle (or Multiple Independently Targetable Reentry Vehicle). It is a collection of nuclear weapons carried on a single intercontinental ballistic missile (ICBM). Using a MIRV warhead, a single launched missile can strike several targets, or fewer targets redundantly. The MIRV system was developed throughout the middle of the 20th century, and one of the main ideas behind the weapon system was to take out an enemy country with a single missile attack before the enemy nation could be able to respond.

For a good example of a MIRV, and possibly the real-world weapon this gun was based on, see the LGM-118A Peacekeeper ICBM system developed by the United States during the Cold War. It was capable of firing one missile which would 'birth' up to 10 nuclear warheads over a wide target area.

Bugs

 * You can enter V.A.T.S. if you have fewer than 8 rounds. It will 'click' 8 times over the course of 20 seconds then exit V.A.T.S. with no action point loss. This can be used for a kind of short term god mode (useful if you're standing next to burning cars, for example).


 * Sometimes, on the Xbox 360 version of the game, NPCs in towns attacked with the MIRV remain hostile after reloading the game. The best way to prevent this is to save outside the town, enter it, blow it up, and load the save. If it happens, rebooting your console may help, as it will clear all data in your console's RAM.


 * Sometimes on the Xbox 360, a graphic error can occur from killing yourself with this. For me, it caused a large, black rectangle to extend from my weapon out to as far as you can see. A simple game restart will fix this.


 * Rarely, when you bring out the MIRV, there will be a Mini-Nuke stuck on the end of the weapon. This does not affect anything, it's just a graphical anomaly. (Observed on PC, needs confirmation).

Entertainment Value

 * For the PC version, open up console and enter "TGM" to toggle god mode, granting unlimited ammo (and removing the need to reload any weapon), invincibility and other fancy stuff. You can get over five shots before the first ones detonate. Use your imagination.
 * Standing on a ledge and firing the MIRV at your feet will launch your character's body (corpse, to be more specific) spinning ludicrously high, sometimes even allowing you to see the outer edges of the map.
 * Try spawning 10 or 20 Super Mutant Behemoths, and let rip with the MIRV.


 * If fired in the Rivet City market it will launch the player through all of the steel walls to the outside and may cause the game to freeze (but it is still worth the hilarious two seconds).


 * If one base jumps off Tenpenny Tower and hits the tower with a MIRV blast, it is possible to fling the player's body to the far side of the RobCo Facility located a distance away.


 * Pause to think. You're doing nuclear rocket jumps.


 * If one jumps off Tenpenny Tower and fires straight down at the ground right before impact, it is possible to fling your character twice as high as the tower.

YouTube Videos
left|Keller Family Tape #5 and the Experimental MIRV

Using the MIRV Skj1jN0oF24

Using the MIRV on godmode by Rowedahelicon dgdQF_ZeUe4