Not that I would ever need this, in fact, I'm more likely to be the one receiving it, but here is a phone number you can give out if you want to get rid of a creep in a bar that wants your number.
http://www.rejectionhotline.com/what.htm
Pretty cruel.
They've got different numbers you can give out depending on what city you're in.
Perfect for people that are into 'one night stands' and don't want the hassle afterwards.
