Press W A X together for all weapons/ammo, keys, a few mines, full map, and last, but not least, full health.

Presdent Mode: corr7 president
Cheat mode: corr7 level1diagnostic -or- -level1diagnotic

Begin a mission, then press Tab-LeftShift-Ctrl for debug mode
Backspace-B Change border
Backspace-C Pauses game and displays useful info
Backspace-F Display your compass angle
Backspace-G God mode
Backspace-I More score, more ammo, more charges, and next weapon
Backspace-M Memory check
Backspace-N No clipping mode
Backspace-R Red skull in front of character
Backspace-T Shows info on current level's transporters [CD ver only]
Backspace-W Warp

When hex editing your saved-game files:
Health is offset 48(decimal)
Ammo is offset 50
Armor is offset 116
Energy for the alien guns is offset 118

Something that I noticed while playing the CD-ROM version is that it knows when you modify your saved games, lets you have the modifications, and then zeros your score... arrgh! I guess that's the price you pay for cheating.