I would be best at history or political science.
My favorite historical subjects are World War II, the American Civil War, the Napoleonic War, sancient, and Christian church history. I could probably fit a few of those in, if I had tenure.
As for political science, I would choose political philosophy or comparative politics. in the former, I could teach the great and not so great political thinker. With the latter comes a lot of international topics of interest.
If I was fortunate enough to become a law professor, i would choose civil procedure. It is a 1l class and absurdly technical rather than theoretical, but i am a geek like that.
You will note all these possibilities are at least on the college level. I do not care how much fun Jack Black was having teaching in School of Rock, I will not babysit a bunch of brats for peanuts forty hours a week plus lesson plans at home. Forget it.