but the most unexpectedly hot scene I remember was a dance in one of the Astaire/Rogers movies, where Fred Astaire offers Ginger Rogers a cigarette afterward, and the audience generally roars, because, yeah. That.

"Night and Day"!

Dance scenes should possibly be in a category of their own.

[edited because I am an idiot]

CYD CHARISSE IN SINGIN' IN THE RAIN.