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.
Completed "Reilly's Rangers"
Completed "Galaxy News Radio"
Completed "Rescue from Paradise"
Completed "The Nuka-Cola Challenge"
Completed "Oasis"
Collected 10 Vault-Tec Bobbleheads
Completed "Tranquility Lane"
Completed "Scientific Pursuits"
Hacked 50 terminals
Completed "The Superhuman Gambit"
Discovered 100 locations
Completed "Those!"
Completed "Blood Ties"
Completed "Big Trouble in Big Town"
Completed "Agatha's Song"
Killed 300 people
Reached Level 20 with Good Karma
Completed "The Wasteland Survival Guide"
Completed "The Replicated Man"
Killed 300 creatures
Reached Level 14 with Good Karma
Completed "Following in His Footsteps"
Reached Level 8 with Good Karma
Picked 50 locks
Completed "The Power of the Atom"
Completed "Escape!"
Took the G.O.A.T.
Got the Pip-Boy 3000
Completed "The Waters of Life"
Completed "Picking up the Trail"
Completed "Finding the Garden of Eden"
Completed "The American Dream"
Completed "Take it Back!"
Completed "Head of State"
Completed "Tenpenny Tower"
Completed "Strictly Business"
Completed "You Gotta Shoot 'Em in the Head"
Completed "Stealing Independence"
Completed "Trouble on the Homefront"
Reached Level 8 with Bad Karma
Reached Level 8 with Neutral Karma
Reached Level 14 with Bad Karma
Reached Level 14 with Neutral Karma
Reached Level 20 with Bad Karma
Reached Level 20 with Neutral Karma
Made one of every custom weapon
Won 50 Speech Challenges
Placed a grenade or mine while pickpocketing
Kill all the Super Mutant Behemoths
Collected 20 Vault-Tec Bobbleheads
Completed "Operation: Anchorage"
Completed "Paving the Way"
Completed "The Guns of Anchorage"
Completed "Aiding the Outcasts"
Completed "Free Labor"
Completed "Unsafe Working Conditions"
Completed "Into The Pitt"
Found All 100 Steel Ingots
Reached Level 30 with Good Karma
Completed "Death From Above"
Completed "Shock Value"
Completed "Who Dares Wins"
Reached Level 30 with Bad Karma
Reached Level 30 with Neutral Karma
Completed "A Meeting of the Minds"
Completed "Walking With Spirits"
Completed "The Local Flavor"
Discovered all locations within Point Lookout
Completed "This Galaxy Ain't Big Enough…"
Completed "Among the Stars"
Completed "Not of This World"
Collected all Alien Captive Recordings