* I loved political science and sociology classes. I would not have predicted that.
* I use my physics classes all the time, but never in ways I would have anticipated. "Hey, I wonder how high we are. Here's a rock we can toss down into that pond. Get your stopwatch!"
* I very rarely find myself working with finite state machines, but when I do, it's nice to feel comfortable reasoning about them.
* Big-O notation? All the freaking time. That's an enormously powerful tool for thinking about how systems will scale with the number of users, for instance.