[quote=Asuras]
True, but I don't believe it was stated that kinetic energy specifically was what is being resisted, just that currently bullets cause bruises instead of holes and profuse bleeding. Superman-like toughness inevitably leads towards being resistant to nearly everything, electricity, acoustics, and lasers included. :p
[/quote]

You're the GM, you get to decide that sort of things... XD
Besides, how many times was superman knocked down by things which reasonably shouldn't have hurt him just for the sake of plot convenience? :P