I was wondering if there really aren't any other words that mean both one thing and the opposite of that thing, though. "Literally" comes to mind, because there's a colloquial use where "literally" is used emphasis and actually means "figuratively": "I made one little comment and she literally bit my head off!" Although dictionaries don't seem to be acknowledging this use of 'literally' yet. Which is okay with me; I don't want to encourage it anyway. >:)
Inflammable comes to mind too, except that inflammable really doesn't mean "cannot be burned" even though it sounds like it should.
Anyway, can anyone else think of any instances?