Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

The Geek (25 points): Complete the game on Recruits difficulty.
Shark Man of the Delta (50 points): Complete the game on Regulars difficulty.
Demo Dick (75 points): Complete the game on Elites difficulty.
SNAFU (5 points): Complete mission 1 on any difficulty.
KISS (5 points): Complete mission 2 on any difficulty.
GNBN (5 points): Complete mission 3 on any difficulty.
PFDL (5 points): Complete mission 4 on any difficulty.
FUBAR (5 points): Complete mission 5 on any difficulty.
HUMINT (5 points): Complete mission 6 on any difficulty.
KATN (5 points): Complete mission 7 on any difficulty.
DOY (5 points): Complete mission 8 on any difficulty.
Double Tap (30 points): Complete an entire mission using only the pistol. (Single Player)
Getting Your Gun Off (30 points): Kill at least one enemy with every weapon in the game. (Single Player)
Frag Out! (25 points): Kill 20 enemies using grenades. (Single Player)
Now THIS Is A Knife (30 points): Kill 30 enemies using kill moves. (Single Player)
Never Knew What Hit Them (20 points): Kill 50 unalerted enemies. (Single Player)
Improv (25 points): Kill 20 enemies using explosive objects. (Single Player)
Guns Don't Kill People, SEALs Do (25 points): Kill 30 enemies using sniper rifles. (Single Player)
Supressing Fire (25 points): Kill 20 enemies using blindfire. (Single Player)
Are These Guys For Real? (30 points): Kill 50 Spetznaz. (Single Player)
Health And Safety (25 points): Blow up 20 fire extinguishers. (Single Player)
Migraine Breaker (50 points): Kill 50 enemies with head shots. (Single Player)
Gang-Bang (35 points): Kill a group of 4 enemies with a grenade. (Single Player)
Dick Would Be Proud (35 points): Complete a mission without dying. (Single Player)
Military Budget (30 points): Kill 5 enemies with an assault rifle without reloading or changing weapons. (Single Player)
Come Get Some! (20 points): Kill 5 enemies with a shotgun without reloading or changing weapons. (Single Player)
Ninja (20 points): Perform 3 Kill moves in a row. (Single Player)
Curb-Stomper (20 points): Perform 5 Finishing moves. (Single Player)
Chop-shop (20 points): Destroy 10 vehicles. (Single Player)
Over The Top (5 points): Throw an enemy over a ledge. (Single Player)
Not The Face (5 points): Smash an enemy's face into a wall. (Single Player)
Fresh Off The Boat (15 points): Play online once. (Multiplayer)
THREATCON (25 points): Place first in a Ranked Deathmatch game. (Multiplayer)
Spec Warrior (15 points): Kill 3 people in a row. (Multiplayer)
SEAL Team Six (10 points): Play a Team Deathmatch to completion with at least 3 friends on your team. (Multiplayer)
Smack The Rogue (25 points): Come first in 10 Ranked Deathmatch games. (Multiplayer)
Friendship Is For Suckers (20 points): Kill someone on your friends list. (Multiplayer)
Keep Your Friends Close ... (20 points): Perform a kill move on a friend. (Multiplayer)
Decorated Veteran (20 points): Play 50 games online. (Multiplayer)
From Beyond The Grave (20 points): An enemy dies from your grenade ... after you have been killed. (Multiplayer)
POTUS (25 points): Place first in a Ranked Team Deathmatch. (Multiplayer)
Special Warfare Group ONE (25 points): Be on the winning team for 10 Team Deathmatch games. (Multiplayer)
Host Me Up (5 points): Host a custom game to completion. (Multiplayer)
Legion Of Merit (50 points): Finish each map in 1st place. (Multiplayer)
One Man Army (30 points): Kill 200 enemies. (Multiplayer)