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