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