Start the game using the command line parameter /cheats=1. The easiest way to do this is by right-clicking on the desktop shortcut to the game, choosing 'Properties', then adding /cheats=1 to the end of the 'Target' Field.

Now during play, press ~ to bring up the console and enter sys cheats 963 to activate cheat mode. Now enter any of the following at the console during play.

cheat lord	God mode
cheat decap	Headless character
cheat teleport	Teleport
cheat suicide	Suicide
sys cheats 369	Disable codes

Turn blood back on:
Open the settings.cfg file using notepad. Change "Violence=2" to "Violence=1". Save, then start the game.

Thanks to Revolution readers Warren, dUKE and Motorman!