A pen holder with the shape of a neuron
This thing is designed using OOML ( http://iearobotics.com/oomlwiki ). If you want to print it just download and print the STL.
If you want to modify it install the OOML (instructions on the wiki) and compile using cmake or your favorite build tool
Source code of this and other things can be found in http://github.com/avalero/3dthings