Is there a current toy craze going on in elementary schools?

What is it? I'm looking for elementary age boys. There has always been toys made popular just because everyone had to have it. The last few years, Pokemon cards, gogo's (crazy bones), beyblades, zhu zhu pets, Kung zhu pets, and the rainbow loom were are must haves around here. And of course there were lots of other famous toy crazes in the past.

I'm shopping for birthday presents for the kids friends and if there is a current hot toy please tell me!