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