Directions:

Head-Set Commands:

"Bravo open/close door"
Say while pointing at a door with your crosshair.

"Breech, Bang, Clear"
Say while pointing at an open door with your crosshair.

"Hands up, get down"
Sneak up behind a guard and say this.

"Team low profile"
Puts the team sneak mode.

"Bravo diffuse bomb"
Say while pointing at a bomb with your crosshair.

"Bravo, Snipe"
Bravo team will snipe all Tangos in view.
(supplied by: ScotlandMaximus)

Unlock list:
Beat the game on the following difficulties to unlock level select, weapons and other difficulties.

Difficulty: Unlock:
Ensign - Terrorist weapons in SP
Ensign - Lieutenant JG difficulty
Lieutenant JG - Level Select
Lieutenant JG - Lieutenant difficulty
Lieutenant - Multiple Grenade Launcher
Lieutenant - Lieutenant Commander difficulty
Lieutenant Commander - Commander difficulty
Commander - Captain difficulty
Captain - Rear Admiral difficulty
Rear Admiral - Admiral difficulty