I had a psychology teacher who suggested that we go into the men's bathroom when there's only one person using a urinal, go up and start using the one directly next to them, and strike up a random conversation.
He also suggested going into an elevator with at least one other person and stand facing the other people in there, preferably while intently staring them down.
I've never tried either of them (and especially not the first one, seeing as how I'm a woman and walking into a men's bathroom would freak guys out enough!), but I like the idea of testing mores and messing with people's sense of "personal space".