Laser cutting a press fit construction kit was a great way to learn CAD. I created a few different geometries in CAD, designed them so they would fit together with or without connecting pieces, and then chamfered them to help with error control and fit.
The construction kit is an excellent desk toy. Right now I use the pieces to vertically store my stapler and some of my pens and pencils to give me more space. I also built a cube and many non-utilitarian designs.
The laser cutting process was easy after watching Nathan and Olga walk through the procedure. The only issue I ran into with the laser cutter was the smell of the pieces afterwords: it took a few hours for my room to stop smelling like burnt cardboard.