Unlockable Modes and Gimmicks

Extreme Ragdoll:           Complete the game once on any difficulty level

Hippy Blood:               Complete the game once on any difficulty level

Level Select:              Complete the first stage, every stage you beat 
                           will be added to the the level select mode

Low Gravity Ragdoll:       Complete the game once on any difficulty level

Massacre difficulty level: Complete the game once on any difficulty level