Simple cube with 18 different holes to connect with cheap wood bbq skewers. The holes are tapered to ensure a tight fit as you push the wood skewers deeper into the block. Using a cheap filament, these will cost about $.10/cube to print (using $9/rolls). The kids use these to build complex towers.

The holes accommodate a skewer with a diameter of 3mm (most cheap skewers are this size). If there is interest or demand, I can create different sizes or variations.