Bauhaus chess set, designed by Josef Hartwig in 1923. The idea behind these pieces was that the design itself reveals the way that the chess piece is allowed to move - thus the L-shaped knights, etc.
These chess pieces can also be used to calibrate 3D printers, as most of the pieces are simple cubes. All of the pieces, including the board square, have negative areas cut out from the bottom to accommodate 12x3mm round magnets or weights. You'll have to adjust the orientation in your slicer for best results.
Update: added an alternative knight (knight_02) that does not have the magnetic base, but is more in keeping with the original design - I noticed on another reference site that the knight actually is designed to be L-shaped on all 6-sides. Unfortunately, that won't work with a center magnet in the base, but it is a more robust design - so it may be worth living without magnetic knights. :)
Update: I decided to create a set of pieces without the cut-outs for magnets. These STL files are all named with the addendum"_02".
Update: Added frame parts for the chess board.
Update: Added hollow versions of all the pieces that can be printed without supports, except for the knight, king, and the top part of the queen. You'll need to flip things around in your slicer to create the proper orientation with the open side facing up. I think I may try printing this set, and then filling the empty space with epoxy to add lots of weight. BTW, the queen is printed in two parts in this version and needs to be glued together after printing.
Update : I'm working on redesigning the frame parts for better fit and to lock together like puzzle parts. I would suggest not printing the frame (red border) parts until the new designs are ready.
Update : Added locking border parts.
Update : corrected the NE corner - do not use Version 3, use Version 4.
Update : added new version of the empty queen - the older version has too narrow of a 'neck' to allow for filling the piece with epoxy. The new version is shown in the photographs.