IFYOUTHINKYOUAREHARDENOUGH 	- All weapons and unlimited ammo
COMEANDHAVEAGO 			- All weapons
NADIAPOPOVXX 			- Level Warp (where XX is 01-34)
TAKEONALLCOMERS 		- Infinite energy

Level Select:
In the password box, type G0LVL and the number of the level you want. (e.g. G0LVL5 and you will go to Level 5).