I'd say that the most overrated degrees are probably STEM degrees, Medicine and Law.
Now, this is not to say that they are bad subjects, or even that I have an issue with people doing them, they're perfectly great subjects. The thing is, in my experience, pretty much everyone at my secondary school wanted to go into these subjects, not because they are particularly interested in them, but because our school provided no support if you wanted to do anything else, so most people thought that they were the only options. Heck, one of my friends who wanted to go into Media, and admitted he still does, suddenly decided that he wants to be a paramedic, even though he hates Biology and finds medical things pretty gross, all because he was taught that anything aside from STEM, Medicine and Law are pointless, and he doesn't think he'd do well in STEM or Law.
Honestly, if teachers actually supported you doing the thing you enjoy as a degree, then there would be no overrated degrees. However, again in my experience, they kick you to the curb if you want to do anything aside from STEM, Medicine or Law, so everyone does them because they're lead to believe that they will have crap, unsuccessful lives otherwise. Plus, this also negatively impacts anyone who does legitimately have a passion for these subjects, because the subjects they take are seen as "overrated," which doesn't necessarily mean anything bad about them, but certainly has negative connotations. Perhaps, over-promoted (by teachers) would be the better word to use.