Nitromethane Jet Bottle - Looks Awesome in 4k Slow Motion - aka Whoosh Bottle

The whoosh bottle is among my favorite demonstrations.

It's easy as pie to set up. It allows some phenomenal chemistry to be shown (limiting reactants, combustion, exothermic reactions, energy transfer).

And it looks gorgeous.

I'm not sure that the nitromethane woosh bottle adds anything cool, but the slow-mo, 4K video definitely does.