An simple octave of piano keys with a pivot area and extended post. Might be neat for a DIY project, where they operate switches or some such.

--- Edit --- Added the 4 different key types as separate objects and orientated in a way that may be more suitable for printing them. (Having a flat surface at the bottom.) Some bits still have a good deal of overhang, so I'd guess they may be one of the more tricky things to print.

Also thinking of having a different style of hinging that uses mounting ears, and adding a catch to the major keys. (Sharp/flat keys already have a catch that hooks on the major keys.) Wouldn't mind seeing any feedback on that idea in comments, as spring loading the keys may make it necessary.