These are things which don’t really fall under any of the other categories I have. They are usually a result of curiosity, flights of fancy, ennui, or displays of one-upsmanship. Some might even be useful…
Quadrotors, n-rotors, and other things that may or may not fly.
Adventures in 3D printing
All aboard the failboat!
Everybody loves FANKART! and the propeller-in-a-pipe.
Glowing decorative safety glasses