Commerce is overrated, particularly at my school. I've taken some econ classes with commerce students and a lot of them seem to think that they're going to be the next 25 year old CEO of some internet company or maybe work at Goldman Sachs and in both cases retire at 35 .... (and all this time a lowly liberal arts student beat them by 20%+ on the midterms). I also kind of hate the attitude that is instilled in them - that every social situation ever is a networking opportunity. It's like, I'm your friend, I've known you for years, and you still leave phone messages and sign your emails to me with your full name (plus the pompous middle initial). Part of me wants to scream "get a life".
Underrated... probably math and philosophy. I've taken courses in both, and although neither of them are my major subject I would love to have time to explore them.