Dissolving Egg Shell
Someone once had me on in a pub that you could pickle eggs by simply placing a raw egg in a jar of vinegar and the energy released by the shell dissolving would hard boil the egg.

When I got back home I put a raw egg in a vinegar filled jar. Immediately air bubbles appeared around the shell as some chemical reaction kicked off.

The shell was completely dissolved in about 3 days. The egg was raw and no doubt gone off since it had been denyed its naturally given vacuum pack, i.e. the shell.