Gene Chao (chair of the psychology department at Berea College) made a wonderful hardwood lathe-turned baby rattle for our new son...when it broke many years later we noted that the end of the rattle, when spun, would invert itself, the frictional torque from the table changes the angular momentum and pushes the heavy side to the top! Here is a 3d printed version of that rattle. Note the asymmetry in the walls of the top...this actually helps the thing invert more easily than a symmetric one.

Print it most easily with the cylindrical side down and the curved side up.