Debug Mode

First, and most importantly, this will only work with the original, unpatched version of the game.
Hit the 'T' key and then type in (case sensitive) ''MasterDebug'' (minus parentheses)
Now hit the asterisk key on the numerical keypad to toggle
debug mode on/off.
While debug mode is activated, hit the tilde key to bring up the debug menu.
There are many things to mess with in here, some of which serve no real purpose, and others which can cause you to have to restart the game in order to regain a playable view -- but there's nothing game-killing in there, really.
There is, of course, a toggle for invincibility, among other things.
You can also pass a command-line option if you wish for debug mode to be active upon startup --
-GCKMasterDebug (case sensitive)
another command-line switch is -nocdcheck, which is (I hope) self-explanatory :)
ENJOY !!

Contributed By: crackerspook.