Unlimited ammo
Start a new game. When the weapon screen appears hold L1, L2, R1, R2, Circle. You should hear a sound like an a laser being shot if you entered the code correctly.

Level 25 Password
OXYGEN

Level 24 Password
ASSERT

Level 23 Password
PHONES

Level 22 Password
DUFFCO

Level 21 Password
SALADS

Level 20 Password
TANUKI

Level 19 Password
GADGET

Level 18 Password
APPLES

Level 17 Password
SHIRTS

Level 16 Password
STAPLE

Level 15 Password
LIQUID

Level 14 Password
ELIXIR

Level 13 Password
STROUD

Level 12 Password
INDIGO

Level 11 Password
BUTTER

Level 10 Password
TEAPOT

Level 9 Password
DUNDEE

Level 8 Password
SQUEAK

Level 7 Password
VOODOO

Level 6 Password
JUNGLE

Level 5 Password
BANANA

Level 4 Password
FINGER

Level 3 Password
BRAINS

Level 2 Password
OCTIPI

Unlock All Bonus Levels
Enter UTOPIA as a password.

Last Level Passwords
Level - Password

26 - JOYPAD
27 - ACTIVE
28 - MENACE
29 - WINDOW
30 - AGENDA
31 - PLINTH