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