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