Quick superhero costumes? A trip to the Army Surplus for some cheap boots and pouches, spraypaint a skull on a black tshirt, and grab a leather jacket, and you've got a convincing Punisher.
Black leather jacket, a black tshirt with a superman logo on it, and blue jeans (or spandex if you're daring), and you can be Superboy.
Draw a ton of tallymarks all over your body and shave your head, and you can be Mr. Zsasz.