The peril of the pick-up.
Addressing the problem. You must be tired, cuz you've been running through my mind all day. If you're looking for a sure fire way to go home alone, use that line.
Back with the ex.
I know people who claim to be best friends with all of their exes. On the flip side of the coin, I know people who've never spoken to any of their exes.
Online dating with someone you already know.
I'll never forget the day a co-worker told me that he'd joined an online dating site and after plugging in all of his information, one of his ten "perfect matches". was me!