This is a fidget spinner. Until last weekend, I had no idea these were a thing. They're the latest toy fad, and are supposed to be beneficial for children who have attention disorders.
This is a three-pronged design. Five pronged versions are also available. They almost remind me of the Glaive, the magical weapon from the 1983 fantasy film, Krull.
By Florian Schäffer - Own work, CC BY-SA 4.0, Link