Click "Play Game" on menu, Then either press " New Game " or " Continue "
Use shift to pause the game and then click on the red skull to enter cheats.

valkyrie - Kill Combo 100 (Once per round)
pantheon - GodHand equipped (Once per round)
rambo - Minigun equipped (Once per round)
adrenaline - Second wind ??
super saiyan - +3000 exp points (Once per game)
i am legend - Kill Count starts at 3000 but no exp for the round.
doom - MFG equipped (Once per round)
ultima - ???
ijohnf - John's head (Restart round)
team meat - Meat Boy head (Restart round)
zombified - Walker head (Restart round)
wtf - all seeing eye (Restart round)