Build a Hollow Analogue Clock
You can never have too many clock projects, and this latest creation by Instructables user shiura is an outstanding example of what's possible with Arduino and 3D-printing.
They've created a hollow clock that moves the hour and minute hands using an Arduino-controlled stepper motor and an ingenious system of gears and parts from the circumference of the clock face that allow for the hands to be moved from the outside, not the centre of the clock.
Truly an outstanding invention - we've never seen anything like this in our life before. Check it out in the following video, and click here to see the build diary and file downloads so you can make your own.