Found another interesting use on one of those "pyromaniacs anonymous" pages - may be an urban legend...

Current WD-40 canisters have a tube coming out of the can, which you plug into the nozzle bit. But old WD-40 canisters apparently used to have a concave top bit with an inset rubber valve, then there was a tube on the nozzle which you pushed into this valve.

Someone discovered an alternative use for this. Since the propellant was quite flammable, you squirted a large quantity into the lid, poured this into the concave bit, lit it, and ran like hell. The propellant would burn, and after a little while (long enough to reach a safe distance!) the rubber valve would melt. The flaming propellant would then drop into the canister and ignite the rest of the can, so you'd get a monster Roman candle effect.

But now you can't do it, cos the can isn't the same. And most spray-cans don't use flammable propellant any more either, so you can't even do the "dragon's-breath" effect. Boring...

Grab.