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