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