T-shirts here. A couple of folks have pointed this out to me recently, so I should note, publically, that I know about it, and I even get some modest payment per shirt sold. That being said, I don't own one myself, and can't vouch for their quality or long-term value. It's the product of a former Princeton grad student. Apparently at Princeton, they all read the PGR, but no one wants to admit it!