Cereal grenades-
Take 1x crow scarer or small banger left over from November...
Take 2x individual size cereal boxes (coco pops/rice bubbles best)
pack the contents of both boxes (minus plastic bags) into one box, insert charge, tape box lid shut.
Light fuze, lob across the anteroom. If you throw high/far enough you get an impressive airburst.
Warning- don't throw at mess stewards (case of flashburns went down like a Lead Zepplin at Taranto night a few years back)
They have the advantage of being small enough to slip into the inside jacket pocket for good surprise benefit!