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