My father was on my case to take typing in high school, claiming I'd need it in the future. I blew that idea off... now 20 years later all I do is type all day!
For me, the most important class I ever took was Electronic Music my senior year of high school. Learned how to splice and edit tape, how to operate a multi-track recorder, work a patch bay, use effects as a send, how to program a sequencer, and we also got some time in on a very early version of Pro Tools. I only record music as a hobby, but it's a hell of a lot of fun (mixed in with some headaches when you're dealing with meh musicians who want their demo to sound like Dream Theater) and almost everything I do now was originally learned as a basic in that class.