Tensegrity Cubes
One of the more interesting designs I found while looking at Tensegrity structures was this cube design where the cubes are strong together in such a way that they float over each other at any angle. The two interlocking cubes lend themselves perfectly well to 3D printing and including string holes in all the corners. The design works well but it's a bit tricky to get the strings adjusted to the right lengths, hence the large knots on the corners. (stl here)
There are two version of the design, one with DIY supports and one without, I'm probably not experienced enough to get my slicer to create supports in the way that I wanted it to. It was also a good exercise in OnShape design, particularly trying to get the cube to stand on one end. (OnShape Workspace)