This is a smaller version of Goette's Kawai Tsugite Joint Puzzle, with the tolerances adjusted to account for the smaller size. The original model was 6x6x3 cm, this one is 4x4x2 cm. I didn't merely increase the tolerances to 150%, I made them even larger because they were pretty tight on the original model. If your printer is very accurate, you can probably print this even smaller without it becoming impossible to assemble.
These can also be used as general building blocks that can be connected in straight lines or right angles.