Our first lab in 2.750: Medical Device Design was a refresher in mechanical engineering fundamentals - designing, calculating, and validating measurements for a kinematic coupling.
Kinematic couplings are really cool - a simple, deterministic way to prevent things from wobbling or be otherwise imprecise in all 6 DOF. One of the professors for the course is really into kinematic couplings, and so of course we the students needed to share in the joy by making some ourselves!
I have to build more gift-pens anyway, so I thought it would be cool to magnetically connect the two halves via a kinematic coupling using buckyball-magnet-toys.
We'll see how my design performs in real life... in ~3 weeks :P