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