A simple airsoft Claymore made from a party popper.
idea found herehttp://www.geocities.com/usafcaptain/claymore.htm
EDIT: The link above is dead. Sorry.
And wow, Its been awhile since I posted this. Since then I've found that, even with corn instead of BBs, this doesn't work except in scenarios where the triggering of the device itself is considered a kill, at which point you might as well leave in the confetti.