Quantum mechanics & general relativity. But not enough ambition to actually do it. And I'm probably not good enough at math. I used to be a lot better at math, I got retarded. Oh, I also want to learn some other languages, like Latin, ASL, Esperanto, German, Sanskrit, French, etc., but again, not enough to actually do it. I learn foreign languages easily, but I also forget them pretty quickly which discourages me from learning.