While playing, press [~] to enter the console, then type any of the following codes:

Code - Result:

ADDCASH - Add Cash
NEXTMISSION - Complete Mission
FAILMISSION - Fail Mission
ROCK - God Mode
GOD - God Mode
GIMMEALLMISSIONS - Cruise Mode
FREECAM - Fly Mode
JUMP - Left Shift to Jump
SPEED - Left Shift for Turbo
TELEPORT - Press R to Teleport
CAMERAEDITOR - Show Cameras
CARCAMEDIT - Move Camera
SETLIGHT - Show Light Settings
SHOWNODES - Show Nodes
SHOWSOUNDS - Show Sound-Lines
EXIT - Exit Game