Unlock the following costumes by performing the corresponding tasks:

COSTUME - HOW TO UNLOCK
Dance - Complete the single player campaign under the Normal difficulty.
Gimp - Kill 500 creatures.
Horror - Kill 100 enemies with a chainsaw.
Mow 'em Down - Get 1,000 total kills.
Red Pajamas - Perform a 150-hit combo
Spartan - Complete the backstory.
White Pajamas - Perform a 100-hit combo.
Wildman - Complete the single player campaign under the Hard difficulty.
Yellow Jump Suit - Kill 100 enemies.