I saw things like these on youtube recently - they are called "fidget spinners", and are for people who need to fidget with something - think the compulsive pen clicker types.  You pinch them by the center bearing, and spin the outer body.  They are actually pretty fun to mess around with - everyone I've showed them to so far has enjoyed fiddling around with them.  I made the one on the left on the CNC machine from bubinga and brass, and the one on the right was made on the 3D printer.