High school:
Favorite: All computer science classes, chemistry and AP physics (had the same teacher for both, he was great!), pre-calculus (another great teacher).
Least favorite: AP English, hands down. The teacher worked us like dogs, with no respect for the fact that most of us were taking 3-4 other AP classes plus 2-3 other senior-level classes. And she had this thing for Tess of the d'Urbervilles. I have a thing for Tess of the d'Urbervilles too - it's called nausea.
College:
Favorite: Holography. That was a fun class. We learned about the principles behind holography, and had a weekly lab. My lab group rocked.

The only problem came with my final project - I was trying to make an animation, but my master hologram plate broke

so when I gave my final presentation, my topic was Murphy's Law. I still got an A+
Least favorite:
- Circuits and Electronics, a required course for all CS majors. Resistors, transformers, capacitors, inductors, all that fun stuff. We had a sadistic professor. For example, one day there were 5 minutes left in lecture, so he said, "We have a few minutes, so I'm going to talk a bit about some research I'm doing." Since it wasn't on the curriculum, nobody took notes... However, it
was on the test.
- Mechatronics, an elective I signed up for. Two lectures in, the prof took me aside and told me he was going to fail me if I didn't drop the class, because I was a CS major, not EE or ME. I hope he didn't get tenure.
- Philosophy, a humanities class (we had to take a certain # of humanities classes). We debated controversial issues like abortion. There were weekly papers. The problem was that if you didn't agree with the professor, he docked you a full letter grade!