Here’s from a reddit-thread on r/mpcnc:
MP Newtonian Reflector Telescope or this Tube Telescope
MP Lab Grade Microscope | Better link here
MP Astrophotography Tracker (Thanks /u/mondoman712!)
MP RC Cars (Based on real cars, too!)
MP Seed Planting Octocopter from /u/armagin and a bunch more MP Quads here and a Micro 105 FPV Quad Here
MP Violin or MP Violin or Fiddle or a Guitar