Start the game with a shortcut with the following command line parameters to activate the corresponding cheat function. Note: Activate the "God mode" or the "Unlimited ammunition" codes before the tutorial is completed (which is after you have delivered the tape to the church) will glitch the game:

CHEAT FUNCTION - COMMAND LINE PARAMETER
God mode - -GameProfile_GodMode 1
Skip introduction sequence - -GameProfile_SkipIntroMovies 1
Unlimited ammunition - -GameProfile_UnlimitedAmmo 1
Weapons never jam - -GameProfile_UnlimitedReliability 1
Unlock all weapons for current area - -GameProfile_AllWeaponsUnlock 1