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