The worst one I ever had was when I went to a party and I met a guy who was divorced but had custody of his child. His chat up line was "S**", do you know how to change a nappy"? When I said No, he said "Do you want to learn"? I ran a mile.
Standing at the cash point after closing time one night, I was approached by what can only be described as a 3 foot troll. My first thought was that he was going to try to mug me (I say try, I would have kicked his ass). Anyway he uttered these magical words...
"I've been watching you all night and was wondering if you would like to come back to mine?"