Inspired by the recent block puzzle from richgain (thing 31639) I decided to recreate a puzzle from my childhood. This came with a booklet with many many different things to build, but of course I don't have that. It can be fun just trying to make the cube.
The SCAD source is parameterized - just two values: 1) the dimension of the small cubes that make up the pieces, and 2) a margin by which to reduce each cube to allow them to fit together. I printed 20 mm cubes with 0.25 mm margin and it worked quite well.