I very nearly got into a "discussion" with someone at a zebra crossing recently.
He had a t-shirt on with an image of Timmy from Southpark - underneath it said "I'm Special".
I think I made it pretty clear, from repeatedly looking from his t-shirt and then making eye contact, that I wasn't exactly impressed. The guy was mid, late thirties, smart, sandals - probably thought he was being cool and ironic.
I'm not the sort for confrontation of any sort - but I really was soooo close....