All Codes
Press ESC then type in these codes:
Kahuna - Add explosions, omniscient view, and invulnerability
Invulnerable - Invulnerable Sarge
Plethora - Full ammo
Occultation - Stealth mode
Aeroballistics - Full air support
Paralysis - Frozen enemies
Telekinetic - Teleport sarge - activate scroll mode first
Triumph - Win scenario
Succumb - Lose scenario
Omnisicient - Overall view toggle
Pyromancer - Right button explosion toggle

Sarge's Heros' Radioactive Explosion Death
In the northeast corner of the desert level Sarges Heroes, if you type in the code (press ESC first) omnisient, you will see little explosion barrels next to a sign that has a radioactive symbol on it. Shoot at them, and a smoking comet-type thing comes at you. You can't outrun it. It drains all your life slowly everytime you spark. If you typed (at ESC) kahuna, your life will stay at 1 little speck.

If you get a instant health, it will either:

a. Bring your life back to full and watch it get drained again.
b. It will immediately go back to 1 speck of life and you will spark like crazy (if you are immortal).