BattleZone

Go to options, then go to the cheat menu. select one of the cheat options and then just type in the code. You just have to move your cursor over a cheat option to select it. If the code is successful you will hear a sound and there will be a "on" icon appear next to the code. When done make sure you press "X" rather than"O" or else all the cheats will be turned off.

Password - Effect

L1, , square, triangle, R1 always invisible
L1, sqaure, triangle, ->, triangle, R1 Insta gib
->, , , , , , sqaure no auto heal
sqaure, ->, triangle, ->, R1, L1 pick up double time
->, ->,