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