Press Ctrl + F11 to access to the Console found in the bottom left corner.

Now enter the following codes, then press enter and hit Ctrl + F11 again

BIONICWOMAN 	- Jump high, but run slow
INVUL 		- Invulnerablitly
LOC 		- Location coordinates on World Map
GORE 2 		- Enhances level of blood
DINOS 		- Freeze Dinos in tracks
BONES 		- Draws bounding volumes for all physical objects
WOO 		- Unlimited ammo
TNEXT		- Transports you through important locations on the level.
WIN 		- Ending movie

Level select:

At the Start screen, hold Ctrl+Shift+Q+W. Then release W.

Thanks to Revolution readers Michael Patten, Dan Barbeau, Grant, and Dave!