Besides the "fire in a crowded theater" example, there's also slander, libel, obscenity, and incitement to violence that are not protected. Obscenity is a very controversial one since there are no clear guidelines of what it actually is (the classic "I know it when I see it" ruling), and as a result it is, as far as I know, very rarely applied. I'd still prefer it weren't on the books at all, but at least we aren't throwing people in jail for swearing.
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SuperNiceDog didn't have to reconcile his name...
But Dauntless Hunter is now MrGreenonion