I'll have to agree with PE. Taking it every so often is one thing - but when I was in middle school, they made people take it for 12 weeks every school year (out of 36 weeks). When I had just started there they apparently wanted us to take 24 weeks of it. Talk about wasted chances, I could've been taking other classes during some of that time I was taking PE. <_< I was so glad when I hit high school and found out I had to take only one PE class for only one year, and that was it.
But as for something that's personally useless to me - higher math classes, especially something like calculus (which I did take at one point). Since I'm studying art, the ability to solve long equations really doesn't help me much, and actually doesn't come up at all. :x So it'd just be a useless skill that I'd eventually forget...and...admittedly have mostly forgotten, ah ha.