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

Don't Tase Me Bro (10 points): Electrocute 35 enemies using the Stun Gun or Taser.
Cowboy (10 points): Accumulate 30 kills using pistols in any level.
Soft Spot (30 points): Accumulate 50 headshots throughout the entire game.
Gives Instead Of Takes Bullets (50 points): Complete the game without dying on Agent or POTUS Detail difficulty.
POTUS Secured (50 points): Complete the game on any difficulty setting.
Yeah, I'm Pretty Awesome (100 points): Complete the game on the POTUS Detail difficulty setting.
Loves Fire, Hates Red Containers (10 points): Blow up 10 fire extinguishers.
No Body Cares (10 points): Destroy 20 busts in Capitol Building levels (Coup D'etat and Filibuster).
Just Like The Real Thing (15 points): Win 30 hacking minigames.
What Are You, A Cat? (50 points): Complete the entire game without ever using nightvision (excluding while gunning in Marine One).
Like Static With Unconciousness (20 points): Zap 75 enemies with the Stun Gun or Taser.
They Shouldn't Have Bunched Up (20 points): Kill 30 enemies using hand grenades and/or the RPG.
The Memory Of A Goldfish (15 points): Kill 1 enemy using the tripwire laser bombs that were set by the Sentavans.
Turns Out They Don't Hail A Cab (15 points): Initiate the explosion of 5 tripwire laser bombs by crossing their lasers.
Too Lazy To Jump And Crouch (15 points): Blow up all tripwire laser bombs in the Rogue Agent level.
Bullet Waltz (20 points): Run for over 3 minutes, crouch 30 times, lean 30 times, and jump 30 times.
Awful Surprise (15 points): Shock 1 enemy with the Taser while they aren't looking.
Some Of Them Still Have Minutes (10 points): Pick up 10 Cell Phones.
Haven't Found A Color I Like (15 points): Pick up 35 Cell Phones.
Opening A Local Wireless Store (20 points): Pick up all 50 Cell Phones.
Countryman (20 points): Beat the game without killing a single Secret Service Agent.
Weapon Tester (10 points): Fire each weapon in the game at least once.
Merciless Speed (15 points): Kill 5 enemies in 5 seconds.
Bow To No One! (10 points): Complete any level without crouching.
From The Hip (15 points): Complete any level without using gun sights.
White House Electrician (20 points): Complete Habeas Corpus using only the Stun Gun and Taser on Agent or POTUS Detail difficulty.
The Best Defense... (20 points): Complete Extraction with more than 50% of the helicopter armor intact.
Master Of Spin (15 points): Win 10 hacking minigames in a row.
Cameraman (15 points): Complete any level without getting hit even once by a turret.
Playing For Keeps (20 points): Complete any level on POTUS Detail difficulty without dying.
Hopefully No Long Term Effects... (10 points): Receive 15 hits from high voltage fences without dying from electric shock.
In Just 30 Seconds A Day (10 points): Perform 5 crouches, 5 leans and run for 10 seconds all in under 30 seconds.
Five Birds With One Boom (20 points): Eliminate 5 or more enemies with a single explosion (use grenades, RPG or Trip Wire Bombs).
Camera Shy (20 points): Destroy 25 turret cameras.
No Record (30 points): Destroy all turret cameras.
Inaugural Assault (25 points): Complete Inaugural Assault on Agent or POTUS Detail difficulty.
Coup D'etat (25 points): Complete Coup D'etat on Agent or POTUS Detail difficulty.
Filibuster (25 points): Complete Filibuster on Agent or POTUS Detail difficulty.
Urban Legend (25 points): Complete Urban Legend on Agent or POTUS Detail difficulty.
Collateral Damage (25 points): Complete Collateral Damage on Agent or POTUS Detail difficulty.
Rogue Agent (25 points): Complete Rogue Agent on Agent or POTUS Detail difficulty.
Habeas Corpus (25 points): Complete Habeas Corpus on Agent or POTUS Detail difficulty.
Last Stand (25 points): Complete Last Stand on Agent or POTUS Detail difficulty.
Extraction (25 points): Complete Extraction on Agent or POTUS Detail difficulty.
Expatriate (25 points): Complete Expatriate on Agent or POTUS Detail difficulty.

Additionally, there are three secret achievements:

Drop The Pin... (0 points): Killed yourself with your own grenade.
Expert Marksman (0 points): Fired an entire magazine without hitting anyone.
The Exact Opposite Of Your Job (0 points): Shot the man you were hired to protect.