(Via) [youtube=http://www.youtube.com/watch?v=cwppgeQQ4sA]
The kick to the groin (never to be underestimated) looks to be the most efficient--altho jabbing the person with the receipt pin appears effective too...if you want to KILL the other person. Although, on second thought, stabbing a person through the frontal cortex with the receipt holder is acceptable punishment for anyone who looks towards Kryptonite's way.