Extra weapons:
Beat the game on "Ensign" difficulty to unlock terrorist weapons. Beat the game on "Lieutenant" difficulty to unlock the Multiple Grenade Launcher.

Level select:
Beat the game on "Lieutenant JG" difficulty to unlock level select.

Unlock Lieutenant JG difficulty:
Beat the game on Ensign.

Unlock Lieutenant difficulty:
Beat the game on Lieutenant JG.

Unlock Lieutenant Commander difficulty:
Beat the game on Lieutenant.

Unlock Commander difficulty:
Beat the game on Lieutenant Commander.

Unlock Captain difficulty:
Beat the game on Commander difficulty.

Unlock Rear Admiral difficulty:
Beat the game on Captain difficulty.

Unlock Admiral difficulty:
Beat the game on Rear Admiral difficulty.

Easy reload:
Press R3 to reload and you won't lose a clip - technically. You'll simply replace the half-empty clip with a brand new one, though you'll still be using up bullets.

Special headset commands:
"Bravo open/close door" - Point crosshairs at door and your teammates will open it.
"Hands up, get down" - Sneak up to guards and yell it.
"Bravo, defuse bomb" - Pointing crosshairs at bomb and your teammates will defuse it.
"Breach, Bang, Clear" - Pointing crosshairs at a room and your team will throw in two bang grenades, and a frag
"Team low profile" - Team sneaks around killing terrorists quietly..
"I got a gun! "What do you got?" "Don't ask don't tell" - Just try them.
"Bravo Snipe" - If Spectre or Jester is carrying a sniper rifle, you can use the command.

Funny convo:
There are two outhouses on level two. One is down by the river, one is close to the Cabin. Blow up the outhouse near the Cabin by planting some C4 on it. If you do it right, Boomer will say,"I guess I'll have to hold it, right sir?"

Game shark codes

Master code (Must Be On)
0E3C7DF2  1853E59E
EE88C72E  BCBF9792

Disable AI
DEB63496  BCA99B83

Thanks to Revolution readers Jeff Hamilton, Greeny, Nick Chu, Import Stylez, JD Mafia, arangers, MG, dave, Rocky, and Fan Wang!