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 Bad Karma
Reached Level 20 with Neutral Karma
Reached Level 14 with Neutral Karma
Reached Level 14 with Bad Karma
Kill all the Super Mutant Behemoths
Reached Level 8 with Neutral Karma
Reached Level 8 with Bad Karma
Collected 20 Vault-Tec Bobbleheads
Collected 10 Vault-Tec Bobbleheads
Hacked 50 terminals
Won 50 Speech Challenges
Made one of every custom weapon
Killed 300 people
Discovered 100 locations
Reached Level 20 with Good Karma
Completed "The Superhuman Gambit"
Completed "The Nuka-Cola Challenge"
Completed "Agatha's Song"
Completed "Oasis"
Placed a grenade or mine while pickpocketing
Completed "Head of State"
Completed "You Gotta Shoot 'Em in the Head"
Completed "Reilly's Rangers"
Picked 50 locks
Completed "Strictly Business"
Completed "Tenpenny Tower"
Completed "Big Trouble in Big Town"
Completed "Take it Back!"
Completed "The American Dream"
Completed "Finding the Garden of Eden"
Reached Level 14 with Good Karma
Completed "Picking up the Trail"
Killed 300 creatures
Completed "Rescue from Paradise"
Completed "Trouble on the Homefront"
Completed "The Waters of Life"
Completed "The Replicated Man"
Completed "Tranquility Lane"
Completed "Scientific Pursuits"
Completed "The Wasteland Survival Guide"
Completed "Stealing Independence"
Completed "Galaxy News Radio"
Reached Level 8 with Good Karma
Completed "Those!"
Completed "Blood Ties"
Completed "The Power of the Atom"
Completed "Following in His Footsteps"
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"
Reached Level 30 with Good Karma
Reached Level 30 with Neutral Karma
Reached Level 30 with Bad Karma
Completed "Who Dares Wins"
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"