8 cubes in a loop; these make a loose fidget that turns around and makes shapes. I like rolling it down a finger. There are two versions in this model, one of them the plainest possible version and the other with one textured edge and a knob on one vertex for more sensory input.

These will often print well with only critical supports.

For a version that is slightly less loose, making for a cleaner turn, but still has space in the middle try the one with bars. The best turning is the thick one, but it has very little space in the middle.  The most impressive is cube in cube which is also a bit larger. If you want something that's difficult to turn, try the one with plates.