Here is the full list of all 34 Battlefield 3 achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
MVP in a ranked match
Completed a round of Gun Master
3rd MVP in a ranked match
Received all 4 weapon efficiency ribbons
2nd MVP in a ranked match
Took your first enemy Dog Tag
Got a kill with the skid loader
Won one round of Tank Superiority
Got 10 kills each with Tank destroyers and Mobile Artilleries
Got 10 kills with each of the ten Back to Karkand weapons
Received one of each ribbon in the game
Destroyed an enemy vehicle using the xbow
Got a kill from the passenger position on a motorcycle
Received all 3 vehicle warfare ribbons
Found the secret reptile
Without dying, got a kill with xbow, primary weapon, and hand grenade
Got a kill with each of the following vehicles: the BTR-90, DPV and F-35.
Got one kill with the Quad bike
Destroyed the Gunship
Got a kill with the following weapons in a single life: Assault Rifle, Jet, Tank
Received all 4 support efficiency ribbons
Fell over the edge on Ziba Tower
Unlocked all xbow parts
Picked up 50 weapons in Scavenger mode
Rank 45 achieved!
Took a swim in the Oman Hotel swimming pool
Won a round in Conquest Domination
Got 10 kills with all ten CQ weapons
Got one kill with the Gunship
Killed an enemy after successfully paradropping a vehicle
Without dying, got a kill with a Carbine, Pistol and Rocket Launcher
Destroyed an air vehicle using the AA jeeps
Captured one flag while playing CTF
Transported a flag carrier in an air vehicle in CTF