Code         Effect  
allmighty    Maximum HP and stamina   
tothepoint   All weapons   
itemsgalore  All items   
doorsnomore  All keys for current level   
levelend     Level skip   
levelheaded  Maximum level gain 

Hints

The Archer:
Even if you pick a character whose skill with a bow is pretty weak, keep using until you become proficient. It really pays off for enemies above and below you.

Thanks to Revolution reader Pete!