Cheats:
 Open up autoexec.cfg file in notepad and change the following 
 parameters, 0 means disabled, 1 enabled:
 
 Code Result
 PlayerTakeDamage - God Mode 
 AITakeDamage - Enemy God Mode 
 PlayerClip - Clipping
 
 Enemies take more damage:
 Note: This procedure involves editing a game file; create a 
 backup copy of the file before proceeding. Use a text editor 
 to edit the "autoexec.cfg" file in the game folder. 
 Change the "AITakeDamage 1" entry to "AITakeDamage 99".