woh boy, strong talk. there are other forums for flaming...but what's wrong with this one
anyways, in all seriousness you could use crackers, but i'd advise against it as the last thing you want is to toss it around a corner and have it blow a players toe off. i know there are mines out there which can be loaded with the lil brass eagle CO2 cartridges as warning devices, maybe mod out one of those.
to be honest though i really don't see the work as being worth it. not to torch or anything, but think about it. the whole point of flash-bangs and the like are to dissoriant and disrupt the opposition and render them unable to fight. you sneak up on a room full of players in a game and throw one of these into the room...
granted you'll get bonus marks for realism, but at the same time you'll be busting through the door with all their barrels pointed right at you.