Right, I might as well tell mine now, since I've been entertained by all of these.
I was in first year in Uni, and I was set up with a girl who, in hindsight, was far too good for me back then (and now, probably). We got to chatting, and were having a whale of a time. After the nightclub, she asked if I would walk her home, and about half way home we started having a bit of a smooch on a bench. As we got up to leave she said suggestively (or so I thought) "Oh, I can't wait to get home". I, being the gentleman I am, pointed vaguely towards a park across the road, and said in my smoothest voice "Well, if you can't wait that long, we could always go......I mean, erm, I've got, erm, some protection............"
It was at that point that I realised that she was looking at me in horror. She started crying and ran off towards home. I ran after her, and after some wailing she explained that not only did she not mean she was in a rush to get home and rut, she hadn't taken to kindly to my ever-so-romantic 'protection in the park' comment. She kept asking why I thought she was like that. We walked home in silence, and she slammed the door shut in my face. Her friends hated me for the duration of Uni.
The worst thing is, I actually quite liked her, and knew she wasn't that sort. Prior to that, I would have been happy with a kiss on the doorstep, so feck knows why I suddenly raised my expectations to sex in a cold, dark, public park.