Enter on the "extra" menu.

Code	                                   Effect               

UP, UP, UP, R2, R2, UP	                 extreme ragdoll
L2, RIGHT, CIRCLE, DOWN, R1, SELECT	     hippy blood
LEFT, RIGHT, UP, DOWN, L3, SQUARE	       infinite health
SELECT, R1, L1, SELECT, R3, L1	         infinite supplies
SQUARE, SQUARE, CIRCLE, CIRCLE, UP, DOWN low gravity ragdoll


Unlockable	         How to Unlock

Extreme ragdoll	     Beat the game once
Hippy Blood	         Beat the game once
Level Select	       Clear one level and you can select it from the cheat menu
Low gravity ragdoll	 Beat the game once
Massacre Difficulty	 Beat the game once on any difficulty