Fallout 3 traps

Traps in Fallout 3 can be found all over the Capital Wasteland.

Cars and motorcycles
Though not a trap in the technical sense, a large number of decaying vehicles can be found around the Capital Wasteland. These nuclear-powered vehicles, suffering from two centuries of neglect, will catch fire and explode if sufficiently damaged (around five hits from a plasma rifle will destroy one outright). When a vehicle takes enough damage, it will release a small explosion and catch fire, giving the player several seconds to escape. Once that period has elapsed, the vehicle goes up in a much larger and more damaging nuclear explosion, similar in appearance and potency to a Mini Nuke. The explosion can be hastened by firing upon the flaming wreck.

An exploding car can be deadly to anything nearby. Anything standing on or next to the car will more than likely be killed instantly. In addition, the explosion may set off other nearby cars, potentially without any delay if the damage threshold is achieved. In areas like parking lots, this can result in up to a dozen simultaneous nuclear explosions.

Though cars are not technically traps, they are used as such in Minefield, which the player will likely first visit during the quest Traversing a Mine Field from the first chapter of The Wasteland Survival Guide. The sniper Arkansas will deliberately fire on the cars from a distance should the player wander too close to them. Being cars, it is impossible to actually prevent this short of killing Arkansas (who will have likely hit them anyway by the time you get in range) or detonating them yourself, as there is no option to disarm them as there is with ordinary traps.

Mine
Frag Mines are commonly laid in areas occupied by hostile forces. They work on a proximity fuse that triggers within a certain distance. Followers will trigger them as easily as the player. The length of the fuse is based on the player's Explosives skill. The greater the skill number, the longer the fuse. They require an Explosives skill of 1 to disarm, meaning any player can disarm one. They can be picked up after being disarmed.

Bear trap
Bear traps are a spring-operated pair of spiked jaws that snap shut on the player's leg should the pressure switch in the middle be triggered. This can cripple the limb at lower levels. A Repair skill of 25 is required to disarm them. Shooting the switch or dropping an object on it also works. Bear traps can be reset, but this requires a Repair skill of 55.

Swing object
Swing objects are simple heavy objects (often a girder, automotive engine, or rotting Brahmin body parts) chained to the ceiling and held up by a trip wire. When the wire is broken, the object swings down and impacts the player for a minor amount of damage. The trip wire requires a Repair skill of 25 to disarm, or the object itself can be grabbed and manually moved to a safe "down" position without any required skill (if it's too high to grab, you can usually trigger it from a safe distance by shooting it). Because of the nature of the trap, it can remain dangerous even after the initial trigger. At certain angles, especially if walked into, it will cause damage, often several times in quick succession. It can also cause damage when manually moved by the grab action.

Grenade bouquet
The grenade bouquet is a cluster of three frag grenades hung from the ceiling. When triggered, either by simply walking into it, shooting it, or hitting the nearby trip wire/pressure plate, the pins are pulled and the three grenades fall to the ground. They explode after a few seconds. Both the trip wire and the grenades themselves can be disarmed, the latter of which requires an Explosives skill of 30. Doing the latter adds the three grenades to the player's inventory. This trap is extremely dangerous, as the combined force of all three grenades is potentially deadly depending on the player's proximity to the blast. They make a tell-tale rattle noise when they fall, alerting players if they fail to notice the trap beforehand.

Pitching machine
Inside buildings, pre-war pitching machines have been set up as weak traps. A nearby pressure plate triggers the machine, which fires about ten baseballs before exhausting its supply. Trip wires will also sometimes operate them. Either part can be disarmed. The danger of the machine lies more in the noise it makes, as the baseballs do very little damage. Any nearby enemies will be alerted by the thunking noise it makes when in operation. An excellent example of this trap can be found in the Arlington Public Library; not only can you be hit by the baseballs in the choke point, but the noise from the trap attracts Raiders.

Gas leak
Gas leaks are areas which have filled with natural gases that ignite if any sort of combustion occurs within the area of the leak. They are usually found in tunnels and can be visually detected by noting a wavering distortion in the air. Anything within the gas leak when it is ignited takes a small amount of damage, is set on fire, and is knocked out for five seconds. This can be particularly dangerous in combat situations if your enemy is not caught in the explosion with you. Guns will set off a gas leak if fired within a cloud, but not from outside. Energy weapons, such as the Laser Pistol, will set off the leak if the shot intersects the cloud at any point (this is noted by a user manual for the Laser Pistol found in the Metro-Central station). (Energy weapons from add-ons do not seem to do this.) The detonation of any kind of explosive (such as a Frag Grenade) within the cloud will also set off the leak. Finally, any item with an open flame, such as the Flamer, Heavy Incinerator, or Shishkebab, will ignite the gas if it comes into contact with the cloud, regardless of whether or not they are actually fired, since the pilot light used to ignite them is active. Holstering them will prevent this. Gas leaks cannot be disarmed, only ignited from a safe distance (energy weapons are good for this purpose).

Pinkerton uses the gas in combination with the grenade bouquet: by triggering the tripwire, the grenades will drop, and the explosion will ignite the gas. However, unless the player did not kill the Mirelurks on the lower level, this is at best a minor inconvenience, as the gas fills the entire hallway and the player will probably have left the range of the grenades.

Radiation trap
Radiation traps are added with the Broken Steel add-on. As the name suggests, they release intense radiation when active. They require a Repair skill of 60 to disarm. Only two locations in the game feature them: Holy Light Monastery, where they can only be activated manually; and Olney Powerworks, where they are triggered as a security measure before you ever get near them and must be shut down using a nearby terminal.

Rigged Shotgun
The rigged shotgun is a simple but dangerous trap consisting of a Combat Shotgun wired to a pressure plate or a trip wire. When triggered, it fires a single blast at the position of the trigger. A Repair skill of 45 is required to disarm the gun itself. Disarming the gun rewards the player with a Combat Shotgun, four Shotgun Shells, and 10 Microfusion Cells (used to power the mechanism which pulls the trigger). Unlike other traps such as grenade bouquets, Combat Shotguns can be disarmed after having been triggered.

Rigged baby carriage
A particularly devious and complicated trap, the rigged baby carriage consists of a Baby Carriage containing a toy baby head with a bomb and several frag mines strapped to it. Upon approaching the carriage, the toy will emit a crying sound (an unfamiliar player will thus approach to investigate) and detonate shortly thereafter with a fair amount of force. This will tend to leave most players wary of baby carriages in the future, despite the rather limited distribution of the trap. It requires Explosives skill of 60 to disarm, and unlike most explosive traps its frag mines cannot be salvaged. Once disarmed, it can be rearmed as a time bomb, or a proximity bomb. An example of this trap can be found in the Meresti Service Tunnel.

Rigged mailbox
Similar to the baby carriage, the rigged mailbox is an ordinary pre-war mailbox rigged to explode if anything ventures too close. If disarmed, the explosive is added to the player's inventory. It can then be rearmed on either a timer or a proximity fuse. You can find one near northwest of The Raid Shack.

Rigged terminal
Another variation on the deadly ordinary objects theme, rigged computer terminals can be found in certain locations. Attempting to use the terminal triggers the trap, causing a slight electrical shock followed by detonation of the main frag grenade inside. It can be recognized by the antenna on the back. The trap can be deactivated by defusing the back panel. Disarming the trap will move the grenade into the player's inventory. The terminal can then be rearmed in the same fashion as the previous two examples. An example of this trap can be found in the drainage chamber near Jocko's Pop & Gas Stop (the source of Signal Sierra Victor) or near the entrance to Pinkerton's hideout in Rivet City. Note that the terminal is just a trap and does not actually contain an interface; using it after it is disarmed only displays a dialog box explaining that it must be rearmed to function, which must be done using the rear panel.

Toilet trap
The toilet trap a simple electrical trap designed to shock anyone who decides to use the toilet (to drink from, in the player's case). 35 Microfusion Cells are in the tank which provide the charge, and are added to the player's inventory if the trap is disarmed. The main example of this trap is found in the Tenleytown/Friendship Station's bathroom nearest the Chevy Chase North exit. A skeleton lying near the bowl serves to warn the player of the danger. Others can be found in the Robot Repair Center and in The National Archives.

Trip wire
Trip wires are thin, easily broken wires suspended a few inches off the floor, usually just behind doors so players won't see the posts it is tied to. Opening the door doesn't trigger it. Players with the Light Step perk can walk over them without fear. They require a Repair skill of 25 to disarm. The player must interact with the posts to disarm it, as the wire is intangible.

Pressure plate
Pressure plates are weight-activated mechanisms set off when it senses pressure from the player stepping on it, thus triggering the associated trap. Bear traps have built in pressure plates. The Light Step perk will allow players to avoid triggering either variety. Pressure plates require a Repair skill of 25 to disarm. The bear trap version can be triggered with a direct gunshot or an object.

Proximity fuse
All mines, including the rigged mailbox and baby carriage, work on a proximity fuse. The Light Step perk will negate this fuse except in the case of the carriage. The only other way to get past it is to disarm the explosive before time runs out.

Usage
Rigged equipment such as computer terminals are triggered by any attempt to use them. A separate area on the object must be interacted with to disarm it.

Remote detonator
The Preacher in Seward Square apparently sets off his minefield remotely. Mines can also be detonated remotely by shooting them, as Arkansas in Minefield is scripted to do.

Video
YouTube video about House of Traps in Fallout 3:
 * http://www.youtube.com/watch?v=VHo8JJKMmVs