Finger surfboard to play on the window of a car. It comes with a little hole at the back in order to tie a string, so you can attach it to your hand and not drop/lose it. Version 4 has a slightly bigger hole, for a thicker string.
If you want to give it a slight curvy shape, you can use a heat gun to slightly soften it, and shape it with your fingers.
Suggested settings for printing:
-PLA, 210/55 (depends on your filament)
-0.4mm nozzle
-0.16mm layer height
-No supports