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
Completed "Strictly Business"
Reached Level 8 with Bad Karma
Reached Level 8 with Neutral Karma
Got the Pip-Boy 3000
Took the G.O.A.T.
Completed "Escape!"
Completed "Rescue from Paradise"
Completed "The Wasteland Survival Guide"
Completed "The Replicated Man"
Completed "Blood Ties"
Completed "The Power of the Atom"
Reached Level 8 with Good Karma
Kill all the Super Mutant Behemoths
Discovered 100 locations
Hacked 50 terminals
Completed "Take it Back!"
Completed "Reilly's Rangers"
Made one of every custom weapon
Collected 20 Vault-Tec Bobbleheads
Killed 300 people
Collected 10 Vault-Tec Bobbleheads
Completed "Agatha's Song"
Completed "Stealing Independence"
Completed "You Gotta Shoot 'Em in the Head"
Won 50 Speech Challenges
Completed "Tenpenny Tower"
Completed "Oasis"
Completed "Head of State"
Completed "The Nuka-Cola Challenge"
Reached Level 20 with Good Karma
Picked 50 locks
Completed "Trouble on the Homefront"
Completed "The American Dream"
Killed 300 creatures
Completed "Finding the Garden of Eden"
Completed "Picking up the Trail"
Completed "Big Trouble in Big Town"
Reached Level 14 with Good Karma
Completed "The Waters of Life"
Completed "Tranquility Lane"
Completed "Scientific Pursuits"
Completed "Those!"
Completed "Galaxy News Radio"
Completed "Following in His Footsteps"
Placed a grenade or mine while pickpocketing
Completed "The Superhuman Gambit"
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"
Completed "Who Dares Wins"
Completed "Shock Value"
Reached Level 30 with Good Karma
Completed "Death From Above"
Reached Level 30 with Bad Karma
Reached Level 30 with Neutral 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"