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