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