A seriously good chat-up line was:
"Hey, do you know where we are?"
Said by my (now ex) boyfriend. We were both lost and he looked really stupid pretending that he was talking on the phone. Then he sat beside me and asked me that question. The funniest thing was, it was the first time I had ever been in that part of the world. He took me home then and gave me his phone number and then we started dating.
So remember that, guys, it'll take you far. May not work at your local Tesco's, though.