Full list of all 72 Fallout 3 achievements worth 1,550 gamerscore. It takes around 60-80 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 5 DLC packs containing 22 achievements worth 550 Gamerscore.
Reached Level 20 with Neutral Karma
Reached Level 20 with Bad Karma
Won 50 Speech Challenges
Reached Level 14 with Neutral Karma
Reached Level 14 with Bad Karma
Completed "Strictly Business"
Completed "You Gotta Shoot 'Em in the Head"
Reached Level 8 with Neutral Karma
Reached Level 8 with Bad Karma
Collected 20 Vault-Tec Bobbleheads
Hacked 50 terminals
Kill all the Super Mutant Behemoths
Completed "Take it Back!"
Completed "The American Dream"
Completed "Finding the Garden of Eden"
Completed "Picking up the Trail"
Completed "Rescue from Paradise"
Completed "Oasis"
Collected 10 Vault-Tec Bobbleheads
Completed "Reilly's Rangers"
Discovered 100 locations
Killed 300 people
Made one of every custom weapon
Completed "The Nuka-Cola Challenge"
Completed "Tenpenny Tower"
Completed "The Superhuman Gambit"
Reached Level 20 with Good Karma
Completed "Agatha's Song"
Completed "Head of State"
Completed "Trouble on the Homefront"
Completed "The Waters of Life"
Completed "Tranquility Lane"
Completed "Scientific Pursuits"
Completed "Big Trouble in Big Town"
Reached Level 14 with Good Karma
Completed "Blood Ties"
Picked 50 locks
Completed "Stealing Independence"
Killed 300 creatures
Completed "The Replicated Man"
Completed "The Wasteland Survival Guide"
Completed "Those!"
Reached Level 8 with Good Karma
Completed "Galaxy News Radio"
Completed "Following in His Footsteps"
Completed "The Power of the Atom"
Placed a grenade or mine while pickpocketing
Completed "Escape!"
Took the G.O.A.T.
Got the Pip-Boy 3000
Completed "Operation: Anchorage"
Completed "Paving the Way"
Completed "The Guns of Anchorage"
Completed "Aiding the Outcasts"
Completed "Free Labor"
Completed "Unsafe Working Conditions"
Found All 100 Steel Ingots
Completed "Into The Pitt"
Completed "Who Dares Wins"
Reached Level 30 with Good Karma
Reached Level 30 with Bad Karma
Reached Level 30 with Neutral Karma
Completed "Shock Value"
Completed "Death From Above"
Discovered all locations within Point Lookout
Completed "A Meeting of the Minds"
Completed "Walking With Spirits"
Completed "The Local Flavor"
Completed "This Galaxy Ain't Big Enough…"
Collected all Alien Captive Recordings
Completed "Among the Stars"
Completed "Not of This World"