A small mechanical counter I designed for archery. Can be attached to a keychain. Will count up to 99. Gears work so the decimal wheel will automatically turn when you go from 9 to 10, 19-20 etc.

You will have to adjust the orientation of some of the parts so they print properly. For the case you will need to use supports for the keychain hole. 
You can use the the images or the STEP-file for assembly. Don't forget to add the second spring in the top half of the case before closing. I used a little bit of glue to hold the springs and the 2 case halves in place.