K		- Kill an enemy
shift K		- Destroy the targeted subsystem  
I		- Invincibility for player's ship    
shift I		- to make targeted ship invincible
9		- Scroll through secondary weapons
shift 9		- Scroll backward through secondary weapons 
O		- Descent style physics
shift W		- Unlimited weapons for all ships

Thanks to Revolution readers Anthony Foster, Will, CK, and Bryan!