BEST teacher? I'd say it has to be a tie between two of my high school english teachers (both males interestingly enough, yet has no bearing as to why the were the best).

Mr. S. taught me to really appreciate literature and Mr. McC. taught me to never bastardize the english language... EVER. He conducted a semester-long intensive study of the parts of speech and to this day I still find myself incessantly double and triple checking my grammar. I also remember him saying he'd been classmates with Sting ("Gordon" to him...) in England. That was pretty cool (at least it was to a bunch of high school kids in the '80s). The guy was as tough as nails as a teacher, but I can honestly say I've never learned more from an individual in my life. Heck, many of my contemporaries can barely construct a sentence lest it be grammatically correct.

And since I managed to work music back into this thread...

BEST rock song you can't help but crank the living shit out of no matter how many times you've heard it.