Type in any menu:

 

"bubbles" - Enables cheats.
 

"thefullmonty" - Turns on level switch capability, use menus to pick any level.
 

"iamzeus" - God mode. Invulnerable, full weapons, unlimited ammo & nitro, 4 powerpods, 2 unknown weapons "SPID" and "THIEF" eyeballs.

"titsoot" - If you have access to the special ship, turns on the "adult" textures.
 

"lumberjack" - This turns on a missile toggle. Hitting quick key for Mug
selects normal, hit Mug again for spiraling Mug, once more for bouncy-Mug. (2 bounces) Hitting quick key for Solaris selects normal, once more for homing plasma like the turrets use, once more for extra powerful blue homing plasma.
 

"jimbeam" - This turns on the beam toggle. Hitting laser quick key selects normal laser. once more for electro-beam like LevTank. once more for superbeam from hades.