Cheat Codes
Start the game with the "-DEVMODE" command line parameter. Then while playing the game, press one of the following keys to activate the corresponding cheat function. *NOTE* All levels will also be unlocked.

Decrease speed: [-]
Increase speed: [=]
Toggle invincibility: [Backspace]
Toggle first and third views: [F1]
Load current position: [F10]
Toggle extra information: [F11]
Advance to next checkpoint: [F2]
Warp to Spawn point: [F3]
Toggle no clipping: [F4]
Return to default speed: [F5]
Save current position: [F9]
999 ammunition: O
All weapons: P

Cheat Code
In the menu, go to additional content, then promotion code, and input.

zUmU6Rup: Unlocks exclusive bonus missions
sa7eSUPR: Unlocks secret missions
tar3QuzU: Unlocks secret missions
THaCupR4: Unlocks secret missions
6aPHuswe: Unlocks more exclusive missions
96CesuHu: Unlocks more exclusive missions
SpujeN7x: Unlocks more exclusive missions