DOOMclone III just got the major v1.3 update that includes a new cheat system. You can find the game at:
http://www.yoyogames.com/games/show/41507

To access the cheat menu, simply press F12 while ingame and enter the code.

Codes (don't include the quotations when entering!):
"gothealth?" - Gives the player 100hp
"gotammo?" - Gives the player 100 ammo
"gotlotsofammo?" - Gives the player 1000 ammo
"imfalling!" - Sets you back to the starting position in the Hell levels, use if the rare forever falling glitch occurs
"killme" - Sets the players health to zero
"hurtme" - Does 33hp damage to the player
"superjump" - Sets the players z value to 150, from which you will fall slowly back to the ground
"tooeasy!" - Sets the difficulty level to 4, in contrast with the nightmare difficulty being 1.75
"toohard!" - Sets the difficulty level to .5, in contrast with the I'm too you to die difficulty being .6
"god" - Sets the difficulty to -2, monsters will now give you health!
"unlock" - Unlocks sectors 3, 4, and 5
"die!" - Destroys all monsters on current level
"secondamendment" - Unlocks all weapons!