We call them singing magnets, buzz magnets, or rattle snake egg. It is a very new style toy.

To toss two magnetic olives into the air, the two magnets fly and collide, wrestling for equilibrium in a clattering, buzzing, Cicada sounding collision until they land in your hands. A pair of powerful olive magnets, their poles aligned through their narrow circumferences, allow you to demonstrate the constant striving of the magnets to stay in perfect balance with each other. Not only are they fun to play with, but also great for hand-eye coordination.