Dungeon Keeper

At the main menu screent type: please give all

There are several bonus stages in Dungeon Keeper, but one of them can be found without doing anything. To access it, set your PC's date to any day with a full moon then start the game. The bonus stage will appear as a flag with a circle in it.

Go into the data file, then open up the creature file and you can change information about creatures and spells around. Ex: You can change the imp spell to where imps cost nothing.