You have less worry about crumbs and grease stains with m&ms, but since my group of old used those for monster minis, there could be some confusion. Also it was the player who killed the monster who got to eat the m&m, so the DM might not like that.I have better Idea. Chips and cookies. You only allowed so many. When you shoot them, you have a 50% of them breaking. So the DM eats them. If you eat them, then you are out of ammo.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.