20 grams of melt-in-your hand gallium for $10

Gallium is a metal that melts at 86 degrees F. It's more fun than playing with mercury, and probably safer, too (it *will* temporarily stain your skin gray though, because it's "wet" when liquid and will adhere to the crevices of your skin). My daughter's friend brought some over a couple of weeks ago, and it was such a hit at our house that we had to get some of our own. This 20 gram sample is just $10 including shipping on Amazon.