Among all the math teachers I've had over the years, one is the clear favourite and one is the least. I'll begin with the bad, and end things on a high note.
I really enjoyed the first real analysis class I took at university. I thought the development of the real numbers was fascinating, and a rigorous view of calculus felt right. I was excited, then, for the third year real analysis class, where we'd be working in R^n. I thought it would be great to learn some of the rigorous math behind what I'd done in multivariable calculus. Needless to say I was left disappointed. What began with high hopes was met with skepticism and my professor stumbled through his lectures, sans notes. While this might've been a manageable situation, the course notes contained hardly any of the proofs which we were discussing in class. Moreover, the professor brought his dog to class on a couple of occasions. Unfortunately a student was terrified of dogs, so the professor had to hold the whining dog in one arm while they tried to lecture on the board with the other. Needless to say his complete lack of effort left most of the class in the dark, and we had to resort to having post-lecture meetings in the math lounge to work together to unpack the results and teach ourselves the course - a silver lining, perhaps.
As these things often do, this teachers reputation preceded them, and my experience was not such a surprise. The lesson I'm left with now is the importance of caring. When a teacher cares, they put a little effort in, and the students will notice. Caring about your students and the kind of learning experience they have, will take a teacher so far from the get go.
My favourite math teacher I ever had was also in university. I took a third year linear algebra class with him, as well as commutative algebra in fourth year. He spoke dryly, and with slight monotone, but as the lecture got going he came to life. He cared deeply about the mathematics he was teaching, and would often pause to prompt the class to join in and ask questions. He would also pause, and give brief historical digressions about the origin of a certain branch of math. He wrote perfect lecture notes in chalk on the board, all without the use of his course notes - which were comprehensive and followed the lectures closely. The homework problems were unique and interesting, and whenever I went in for office hours he would take more time than he needed to help me, answer my questions, and discuss mathematics outside of the context of the course. It was through this teacher that I saw the beauty of the deeper side of mathematics which I felt like I had been pursuing throughout my degree. Even so, he opened my eyes to the world of mathematics and I realized I was barely even scratching the surface. This experience left me with a sense of awe and wonder at the brilliance of humanity, and all we could achieve when we put our mids to something.
This feeling of wonder is something I hope to impart on my students one day. I want them to feel like it's a big world out there, but they're capable and ready to take it on one little bit at a time.