This is a liberated game: it was originally shareware, but in May 2007 Apogee Software/3D Realms released the full version as freeware.
Full health and power: Pressing the B-I-G keys at the same time will give you full health and jetpack power.
The following cheats work on version 1.1 of the game or higher:
Ctrl-R-E-N: Gives you all weapons, and activates god mode for several seconds.
Alt-L: Level warp. After pressing, type the number of the episode (1-4), then the number of the level (1-5). Incorrect input will crash the game!
Alt = Change location within a level. Type coordinates after this code. Incorrect input will crash the game!
Description by VGTips