Today, while packing for my upcoming move, I found a bunch of notebooks from college. In between taking notes, I would often turn to the back on a notebook and start writing random things. Often, this took the form of a list. I had apparently forgotten just how geeky these lists were. Today, I found all 43 recurring or regular characters on Buffy, all 13 Beatles albums, all 16 Martin Scorsese movies I had seen at the time, and (then) all 38 members of the Justice Society of America. Each of those lists, and dozens of similar ones, were ranked in order of my personal preference.
So that was what I did for fun in college. Currently, I'm making a note reminding myself to not do the same thing in graduate school.