My favorite class in grad school, and also my favorite science class (without quite as many strong contenders) was probably Nick Warner’s general relativity course at MIT. I was a grad student at the liberal-arts college up the river, but Ted Pyne and I happily hopped on the Red Line twice a week to attend this course, given the sorry state of Harvard’s GR offerings at the time. This was a big lecture course, with detailed hand-written notes handed out beforehand, and there wasn’t too much in-class discussion — Nick talked awfully fast, and it’s not easy to stop that much momentum once it gets built up. (But there was a weekly recitation where we could ask whatever crazy questions popped into our heads.) Every week we were pushed to the limit, and loved it. We must have loved it, as Ted and I taught our own seminar to our fellow grad students the next year, and I went on to teach the course as a postdoc, and then as a professor, and write up my own notes, which eventually made it into a book. In the foreword of which, Nick gets a hearty acknowledgment.