Chess clocks / microprocessor controlled units are awesome. Originally a chess clock is what inspired the idea.
That said, I don't even know where you would buy a chess clock, and microprocessor controlled units are more expensive and complicated.
All of these items, save for perhaps an ammocan but tupperware would work, can be acquired at any dollar store.
"Hokey religions and ancient weapons are no match for a good blaster at your side" - Han Solo
Commanding in Airsoft