Press ~ during game play to display the console window. Then, enter one of the following codes to activate the corresponding cheat function:

Effect - Code

999 ammo - allammo
Disable collision detection - ghost
Disable CPU AI - playersonly
Flight mode - fly
God mode - thematulaaklives
Set game speed - slomo
Skip to next load screen - darman
Spawn explosives most secondary weapons, and ammo - loaded