Head support for Shermers neck
Shim for light/computer/pump clamp that might be a bit big.
Strap for holding things to a rack.
gasket making material.
makeshift rubber bands
I have taken a valve off one and soldered it into an old fire extinguisher to make one heck of a squirt gun (with a noise that will scare the crap out of anyone down range as well).
I'll post more if I remember them but inner tubes are almost as useful as duct tape.