Indestructable Sport Sunglasses. See them TIED INTO A KNOT here:

Yes, I know. It is unbelievable. And until I saw it in person, I just thought it was a marketing thing. But you REALLY can pop the lenses out of these, tie them in a knot, put them back together and put them on. Available Here:
The story goes that, in 2002, the founder of Numa [...]