Invincibility 
Pause the game and press 
Square, Circle, L1, R1. 

All weapons with full ammunition 
Pause the game and press 
Square, Circle, R1, L1. 
Enter the code again to refill ammunition. 

Tin foil uniform 
Enter TNMN as a password. 
This is not an armor, just an effect.

Level passwords
 
Level+Name -- Password 
2 Bridge -- FLLNGDWN 
3 Fridge -- GTMLK 
4 Freezer -- CHLLBB 
5 Inside Wall -- CLSNGN 
6 Graveyard -- DGTHS 
7 Castle -- FRNKNSTN 
8 Tan Base -- BDBZ 
9 Revenge -- LBBCK 
10 Desk -- DSKJB 
11 Bed -- GTSLP 
12 Blue Town -- SMLLVLL 
13 Cashier -- CHRGT 
14 Train -- NTBRT 
15 Rockets -- RDGLR 
16 Pool Table -- FSTNLS 
17 Pinball Table -- WHSWZRD