My own version BB-8, the new droid from Star Wars: The Force Awakens.
Check-out the video for a demo and overview of the assembly process.
It's powered by an Arduino board and remote controlled via RF. This droid self-balance on two wheels, play sounds, and has several programmable LEDs.
Advantages of this version:
This BB-8 was entirely designed in SketchUp. The head is printable in one piece of 11cm in diameter, and the body is divided in 8 pieces of 10x10x10cm. Here are the STLs:
The SketchUp plugin Solid Inspector² was really useful to find common 3D errors in your model that would make the slicing process difficult for printing.
Once the mesh is clear of bugs, I used the STL file Exporter plugin to export STL files to the slicing software.