I got some stories....
Sometimes get the train to work and back. This one time, there was a free seat opposite what looked like a young couple. I was 23 at the time. The guy looked 18 and the girl slightly younger. I only assumed they were a couple because they were sat next to each other, despite the seat I was now sat in free.
The guy was asleep, and the girl kept eyeing me up and smiling. I didn't know what to think. The guy woke up at one point and was like "****". He then called someone on his phone and informed someone he fell asleep on the train and missed his stop. He then got off at the next station. That was when we started talking. We basically just laughed about it, I was saying that I thought they were travelling together.
She was kinda cute, but I had no idea of her age, so may have been a bit risky to actually start chatting her up.
Another incident; this fat school girl and her 2 mates sat at the same table as me, complaining about a drunk on one end of the carriage. I had ear phones in, and they thought I wouldn't be able to hear their conversation... But I did. They started talking about me (nothing suggestive, or mean) and when one of them said "Do you think he can hear us?" I took out my ear phones and replied 'yes'.
We then started talking (I can't remember what about) and they asked how old I was (23 at the time). The fat one was leading the conversation and the other 2 friends were like "You're only 15" to the fat one, as if to say she was trying it on with me. When the conversation went dry, I put my earphones back in and stared out the window. They waved to me as they left.
Another time, I sat opposite these 2 lovely looking girls, listening to my music. The prettier one wouldn't shut up about how she got an interview with some celebrity for her radio show. Would have been too far up her own arse to start chatting up. Plus, I'm not confident and cheesey enough to actually make a move on a random stranger I just met on the train.