Hex Cheats:
Use notepad or a text editor to edit the autoexec.cfg file

Change the following

Invincibility:
Change "PlayerTakeDamage" "1" to "PlayerTakeDamage" "0"

Enemy Invincible:
Change "AITakeDamage" "1" to "AITakeDamage" "0"

No Clipping Mode:
Change "PlayerClip" "0" to "PlayerClip" "1"

Enemy takes ALOT of damage:
Change "AITakeDamage" "1" to "AITakeDamage" "99"