i don't think I've ever dressed ugly intentionally. I'm not saying I'm "intimidating" but IF I were to some people than I would not care if I was. its not just the looks its the attitude you're carrying that would make someone look intimidating. also, beauty is in the eye of the beholder.
The problem with that is if no one thinks you're good looking, they probably won't care. Ugly people don't get approached because they're not attractive. Good-looking people get approached sometimes, but are intimidating to many. I'd much rather be in the lattter situation.
i have gone out not caring what I look like for example track pants to the mall but never intentionally dressed ugly for the sake of it