I'm patiently waiting for my new 3D printer to arrive. I've got a load of accessories for the printer setup, I've got an Arduino to help flash a bootloader and install some new firmware, and now I'm looking for hacker projects to print on it. Aside from adapters for the house (vacuum, etc), what do you all suggest?

I'm looking at the Digispark boards right now, thinking of making my own USB rubber ducky, but I'm curious what others would do.