My new favorite t-shirt:

It’s a stellated icosahedron from Henry Segerman, who makes many interesting nerdy things, inspired by both math and juggling:

• Henry’s mathematical art at Shapeways, of which there are too many cool things to mention, except I have to mention Rubenstein’s Cactus and 3 Club Cascade Motion, but really, look at all of it!
• Henry’s shirts at NeatoShop, where I bought my stellated icosahedron shirt.

BTW: stellation is the process of creating new shapes by extending the faces of a polyhedron. The shirt is a stellation of a regular icosahedron (known in gaming circles as a D20). The logo for this site is a stellation of a regular dodecahedron.