Fallout 3 Cheats

The Superhuman Gambit (Bronze): Completed "The Superhuman Gambit"
The Wasteland Survival Guide (Bronze): Completed "The Wasteland Survival Guide"
The Waters of Life (Bronze): Completed "The Waters of Life"
Those! (Bronze): Completed "Those!"
Tranquility Lane (Bronze): Completed "Tranquility Lane"
Trouble on the Homefront (Bronze): Completed "Trouble on the Homefront"
Vault 101 Citizenship Award (Bronze): Got the Pip-Boy 3000
Vault-Tec C.E.O. (Gold): Collected 20 Vault-Tec Bobbleheads
Weaponsmith (Silver): Made one of every custom weapon
Yes, I Play with Dolls (Silver): Collected 10 Vault-Tec Bobbleheads
You Gotta Shoot 'Em in the Head (Bronze): Completed "You Gotta Shoot 'Em in the Head"

Infinite XP
You can gain infinite XP if your speech skill is high enough. (My speech was about 30 at the time). Go to town called "Big Town" located north of Vault 101.If you spoke with a girl named Bittercup she should tell you about her dating exploits. After speaking with her, go into the house marked "Common House" and speak to a man named Pappy. There should be a speech skill dialogue option that says "You came here with Bittercup, right?" You will get XP every time you click it. (I got 6XP with each click). Continue to do this and you can rack up XP in mere seconds. Bethesda has not yet patched this glitch.

The Replicated Man quest: Get both rewards
When you discover the identification of the android and are deciding to turn him in or warn him, go to the android first. Convince him to go to Zimmer on his own and he will reward you. After that, go to Zimmer in the science lab. Tell him about the android's identity. He will also reward you. Note: You will still get bad karma.

Finding Dogmeat
Dogmeat is found in Scrapyard. On the world map, Scrapyard is in the top right corner of the square that is two squares directly below Minefield. Follow the clear triangle on your compass if you are having problems finding it. Go into Scrapyard and look/listen for fighting. Your will find Dogmeat fighting a Raider. Once the Raider is dead you can talk to Dogmeat and ask him to join you.

Easy caps
Note: Only proceed if you want to take the "evil" path. After agreeing to help Mr. Burke nuke Megaton, go into every single house and steal everything (any little piece of junk you can carry). Sell them to the local shops (Craterside Supplies, The Restaurant, Moriarty's Saloon, etc.). If a particular house is locked or you need a key to get into a safe or something of that nature, simply kill the owner of said property and get the key from his or her body. Kill everyone in sight, especially the shop owners because you can get access to their entire inventory, plus the caps that you have already spent on them. Kill every one and collect everything to leave Megaton empty. You should have at least 600 caps. Remember to sell some of the things you gather to the shop owners because you cannot fast travel when over encumbered. This can be done in almost any town you visit. To avoid getting over encumbered, get all the supplies that you can possibly carry, then drop the rest just outside of Megaton. Fast travel to Rivet City or some other marketplace. Sell what you have, then return to Megaton and repeat the process.

Fabian Solis
Save all pre-war books you found (not scorched or ruined). Go to the Arlington library. At the southeastern corner you can find an NPC that will buy those books for 100 caps each. You will also get 10 experience points for each book you sold.

Easy Stealing, Hacking, and Speech bonuses
Save the game before starting a dialogue with a Speech bonus, hacking a computer, lock picking, or pick pocketing. Simply reload the game if you fail the challenge.

Lock picking
Use the following trick to avoid breaking bobby pins when trying to pick a lock. Just before the bobby pin is going to break, exit that screen then go back. You will save a lot of bobby pins by doing this. This also works when trying to get a password for computers.

Sandman Glitch
This a glitch for getting infinite exp Steps: 1.) Reach level 10 with a sneak skill of 60 and get the Mr. Sandman perk. 2.) Go to Andale (south central part of the map) 3.) Wait until around 1am and go into the Smith house while they are sleeping. 4.) Go upstairs into the kid's bedroom 5.) Use sandman on him (crouch and select him and and use the first option) 6.) Repeat step 5 7.) Increase difficulty for more XP.

Super Mutant Behemoth locations
There are five Super Mutant Behemoths that can be found and killed. After they die they cannot respawn. You can find them at the following locations.

Galaxy News Radio: This Behemoth will destroy a wall just outside the GNR Building as you enter the area (quest related).
Evergreen Mills: At the bandit camp near Vault 112, a Behemoth is behind an electric enclosure beside the train tracks. When the generator powering the enclosure is destroyed the Behemoth will escape.
The Capitol Building: Use the west entrance and go inside the main room. Look on the map. The room is straight down the hall from the entrance. However debris will force you to find an alternate route there.
Takoma Industrial: Located east of the GNR Building at the end of the map. The Behemoth is just north of the factory, standing in the middle of some wrecked cars.
Jury Station: Go west until you find a group of crumpled up train cars. Search this area until the Behemoth appears. You will know if you are in the correct area if you see a teddy bear in a shopping cart.

Infinite Experience in Big Town
Here's a glitch that will allow you to get infinite amounts of experience (as long as your Speech skill is high enough). Try the following steps:

1.) - Go to Big Town and find the NPC named Pappy.

2.) - Select the dialogue choice “You came here with Bittercup, right?” If this dialogue choice doesn’t show up, find Bittercup, exhaust all of her conversation chains, and then try speaking with Pappy again. ([Speech 100%] should appear next to the dialogue choice if your Speech skill is at its highest. If it’s not there yet, don’t risk trying to convince him. Speech failure will result in this glitch permanently disappearing.)

3.) - Selecting that dialogue option successfully will net you six experience points. Speak to him again and you can get the experience again. Repeat as much as you want for as much experience as you want.

V.A.T.S. Spotting
If you’re heading into seemingly-hostile territory or simply want to survey the area around you for enemies you might not yet see, try hitting the VATS button over and over again as you make your character turn around, searching all angles. Doing so will alert you to any enemies you may not yet see by zooming in on them in VATS mode. You’ll realistically be unable to do damage to your foes from such a distance, but it’s a good way to spot foes before they spot you so you know what you’re getting yourself into before the crap hits the fan.

Hacking Indefinitely
Here's a great tip (though it will be obvious for some people).When you hack a computer in the game, you have four tries to hack it successfully. If you don’t hack it successfully on the fourth attempt (as in, you don’t guess the proper password), the station you’re trying to hack will permanently shut down. But if you only try three times and bail out of the process before trying for a fourth time, the password will reset, giving you three more options. You can do this indefinitely without risking shutting the terminal down.

Extra Inventory Space
If you're running out of room in your inventory and don’t want to ditch any of your gear, consider trying to find a companion character. These companions can be found at various places throughout the world and will agree to join you on your journey (temporarily). You can trade equipment with these characters, which will allow you to dump your equipment on them, making you virtually unencumbered. Consider this option when you not only need help with bad guys, but help carrying your crap as well!

Unlimited Items
If you have a sneak rating of at least 60, you can attempt this infinite goods trick, which takes place at Fort Independence. Head to Fort Independence with a bunch of Scrap Metal in your inventory. Once there, speak with Protector Casdin and tell him you’ve got junk you’d like to give him. In return, he’ll offer up 5.56mm Rounds, Frag Grenades, RadAways, and Stimpaks, and you can choose which you want. Then, save your game (in case you fail the following) and steal your Scrap Metal back from the Protector. Sell the Scrap Metal back to him over and over again, thereby netting you infinite amounts of 5.56mm ammunition, Frag Grenades, RadAways and Stimpaks.