Press F10 during game play, then activate the following cheats by entering the corresponding codes. Note: Most of the following codes will work with the original, unpatched game. Some codes will be disabled in the patched versions of the game.

CHEAT FUNCTION - CHEAT CODE
All weapons and ammo - winblows
Display message [NOTE 1] - goldmode
Dynamite - tntrules
Elephant gun - dumbogun
Enable bigboom code - headofhorrors
Extra ammo - moreammo
Flame thrower - torchmyass
Flaming tip arrows - burningstake
Gas mask for stranger - ifarted
Gas mask - youfarted
God mode - godgames
Instant kill1 - bigboom
Radiance Emitter - amonra
Rain - thunderstorm
Recharge battery - recharge
Restore health - healme
Shotgun and/or 500 shells - shotgunshell
Skeleton key - skeletonkey
Snow - snowstorm
Stranger wears alternate hat - oldhat
Summon Baron - baronsaturday
Toggle enemy AI - freezer
Toggle gratuitous dismemberment - goremode
Tommy gun - driveby
Wooden stake crossbow - woodenstakegun

NOTE 1: May kill one or multiple nearby opponents. Repeat to kill survivors. The headofhorrors code may need to be enabled before this code works.