This awe inspiring geometry is known as a sphericon. It has a single continuous surface that makes it roll along a very curious wobbly path. This version is modified to have a sloped surface that looks extra sleek without affecting the performance.
Download includes the full model, and a split version optimized for FDM printing. The center connector piece may need to be scaled down 1 or 2 percent depending on your printer... or you can just glue the halves together!
This can be printed with a 5% infill, but the heavier it is, the better it tends to roll, so a solid copperfill version would be pretttty cool ;)
Scale however you'd like
Pictured model printed in MatterHackers Translucent Red PRO PLA
See my video of these in action here