During play, press F12 and type imarealweenie, then press F12 again to enable cheat mode. Now press F12, enter any of the following, then press F12 again to activate.

enemies              See enemy hit points   
sight                See line of sight   
spy                  See debug information   
makethemstopmommie   Disable enemy AI   
hidetext             Disable text   
fps                  See frame rate   
mapmaker             See .BMP format map   

Kill all enemies:
This one is a little tricky. Press F12, then type wtswwt-bgiob and press Enter. Now press F12 again, type imarealweenie and press Enter.Now during combat, press Ctrl + F3 to kill all enemies.

Thanks to Revolution readers Tom T. Chen, Zero, and Robin ionacode!