1. a picture of a Rubik's cube subwoofer. (They're only making 200, so I could never afford one.) This was actually in the magazine in my hotel room, so it's really just a coincidence.
2. An actual copy of Flajolet and Sedgewick's book Analytic Combinatorics. (Cambridge University Press had a display table.) I was not the only person who didn't believe it was actually a book. (In fact, Sedgewick seemed a bit surprised.) It appears to be very nice as a physical object, and in particular is surprisingly un-brick-like for an 800-page book.
3. A bunch of talks, many of which were interesting. I may have more commentary on the ones I found particularly interesting once I read the associated papers.