Access the PC console by pressing the tilde key, then enter the following cheats as you wish.

give all - All weapons
sf_use_bw 1 - Black and White movie mode
devmap [map name] - Change maps
notarget - Disable AI
god - God mode
sf_use_ignoreammo 1 - Infinite ammo
mapname - List maps
noclip - No clipping mode
sf_use_invert 1 - Photo negative mode
sf_use_chaplin 1 - Silent movie mode