Here is an experimental smaller version of the popular Steady State cube based on 3mm unit cubes.
In White Strong & Flexible it works well and looks really great when the pieces are dyed in different colours.
Shapeways successfully printed this in metal for me but the roughness of the metal surfaces made it impossible to fit the pieces together at first. After some careful Dremel work all of the surfaces are now smooth and the puzzle can be assembled correctly. However, this did take a significant amount of work and I would not recommend ordering this puzzle in metal unless you are prepared to take on the necessary post-processing work.