During the game press [Enter] and then you might type in:

 +sniper               - 100 meter range for ranged weapons
 +potionaholic         - 3 Super Health and Super Mana Potions
 +zool                 - Invincible (needs to be entered after every cutscene)
 +checksinthemail      - Max gold
 +drdeath              - Max out all stats
 +sixdemonbag          - Powerful summon spells