Following Lono's comment on the "Artsy people piss me off" thread, (something about farting on someone's leg ) I thought that this would be an interesting thread. I personally don't like talking to strangers so a good brush off is very nice to have.
So post ways to brush people off, realistic, or hypothetical.
Mine: I am in Germany right now learning German, so if someone asks me anything I can just bust out in my worst broken German and say that I don't understand them. That ends the conversations real quick whether I actually understood them or not. hehe. Very handy considering that many Germans are really talkative and will not think twice about striking up a long-winded conversation with you.
Or I just say next to nothing, so that they lose interest. Works without insulting anyone.