Various Codes:
TWISTEYE    Rotate the screen by holding L1 + L2 & moving the D-Pad
INANDOUT   Quitting returns you to the map
THETHING    Hold L2 to mutate your body. Press L2 + X to reset
HARDBODY Invincibility
BODYSWAP Press Triangle to swap characters in mid-game
VITAMINS     Gain 31 Lives
TOMMYBOY Takes you to a pinball screen when you finish a level.
CASHDASH Takes you to a 'Speed Greed' screen when you finish a level
BORNFREE Level Select
ALMABHOL Open All Levels
CORONARY Plenty Of Hearts To Keep You Healthy
EVILDEAD    Immortal Enemies
OTTOFIRE    Special weapons never run out of power
KNCACKDE Bonus Pinball round

Level Passwords:
These will take you to any level with no goodies -
1    ADEAMIIE
2    EPIJAKCA
3    FBIJAKCI
4    KOCCCIEE
5    NGIAIBJJ
6    NIIAJBCB
7    KGCACICI
8    AHICBAJE
9    AIICFAJG
10  AIICBAJI
11  FBIIAKCK
12  FDIIAKDC
13  FFIIAKDK
14  KACACIBA
15  ADMCFAID
16  EMIIEKBE
17  OEIBIBMJ
18  FAAIAKCE