By 
Get your dagger out, throw away any secondary weapon you have, pause the game and enter the code (In the pause screen)
Left, left, right, right, up, down, down, up, up, down Baby Toy Hammer (I think you get the code from Easy mode)
Up, up, down, down, left, right, left, right, up, down, up, down Chainsaw (Gotten by completing Hard mode)
Up, down, up, down, left, right, left, right, up, down, up, down Swordfish (Code distributed with premium version)
Right, left, right, left, down, down, up, up, up, down, up, up, down, down Telephone of Sorrow (Gotten by completing Medium mode)
