I could go on for *days* ...
I took a philosophy course once, figuring that as long as I could write a good argumentative paper (and I can) defending either side of an issue, I'd be ok. WRONG. One of the issues we discussed was abortion. We had papers due every week, and we discussed this issue for a month. It was interesting how my grades went up by a full letter grade when I argued one side of the issue vs. the other.
Then there was the prof who got hold of our student evaluations before the end of the semester, against all school policies. I'd given him a negative evaluation, because this guy couldn't teach his way out of a paper bag open at both ends. So he told me that I'd better drop his class or I *would* fail. And he tore up my evaluation form - I know this because he got a glowing write-up in the next student evaluation summary, that stated he was "unanimously popular".
If I hadn't been applying for grad school there at the time, I would have gone to the department head. I just hope he didn't get tenure.