Almost all of my male history teachers. One looked like an older Robert Heinlein, another looked like a groomed Mark Twain, but there were some younger guys, too.
Mr. C was the one I really wanted - my sophomore world history teacher in high school. Late twenties, lean, obvious geek ... in fact, a less-scruffy version of David Tennant as the 10th Doctor, now that I think about it. He knew everything
about history, and he and I would have discussions during free time in class about this, that, and the other in the subject. I even asked him to edit an historical novella I was working on at the time. He did respect my intellect, though, and was impressed with my work - even if his eyes were in my cleavage a lot. I think we were both tempted, to be honest, and the only things keeping us in line were his position and my age.
Ironically, his girlfriend (whom I saw once) was also a busty redhead who wore glasses and had a Ph.D.