Type at the main menu or during game play:

Effect - Code

Toggle AI debugging - debugai
Toggle All debugging options - catdebug
Toggle cheat mode keys - iamacheater
Enable game debug mode - gamedebug
Enable engine debug mode - enginedebug
Toggle safe mouse pointer - safemouse
Ground type editor - bedit
Enable movie capture - moviecapture
Enable CatEdit game editor after entering engine debug or game debug mode - catedit