The Smiths Tubes Cannon - Chew up one Smiths Tube until it's good and spitty, then using a second tube like a pea shooter, blow globs of masticated potato at fellow diners.
Sadly, Smiths Tubes are no longer with us, but I'm confident that this will definitely work with Golden Wonder Wheat Crunchies.
The Long Wotsit - Take some Wotsits and nibble a small piece off each end. Using enough saliva, the Wotsits can be pressed together to make a single freakishly long cheesy stick. This will invariably lead to somebody declaring, "that's no Wotsit", in an Alec Guinness voice and then a dinner lady will gasp and faint.

Wheat Crunchies also make excellent smoking receptacles. You look like a true spiv.