Lady sitting opposite me on the train the other day - pretty, well-groomed, but chewing gum with her mouth open - which, IMHO, made her look a lot less attractive.
I'm not against gum chewing per se; I don't like doing it myself, but each to their own. However, I can't help think that chewing it with the mouth open makes a person look gormless / arrogant / like they don't care / attitude-y. (Note I say it makes them appear like that, not that I think they are that.). I just think it's horrible!