There have been two for me. One from college that was just incredible looking. Every time I locked eyes with her my legs would give out. I had been chasing this girl for a while and she showed absolutely no interest. After a while I decided to move on and started talking with one of her friends. Of course then she decided she was interested in me and asked me out. The day we were suppose to go out one of her friends had a hangover(and no it was not an excuse) and she had to stay with her...we ended up not going out, I was mad and stopped talking to her. She started dating a guy soon after this occurred and they ended up getting married. To this day I still have those feelings for her when I see her...pretty sad.
Second was a girl a few years after college. We were set up on a blind date and the initial date we hit it off. We talked for a while and went out again and things seemed to be going good. She then stopped taking my calls and I just figured that she wasn't interested so I stopped calling. She was the lead singer for a local band and I was at a bar one night when she was performing. I stopped by and said hi, and she asked why I stopped calling and said to call her the next day. I called and she didn't answer, I left my # and told her to call me if she wanted to get together...she never called and I never talked to her again. just weird, I think she liked the fact that I was attracted to her but she didn't actually want to talk to me or something....I never have understood women.
both women were way better looking than me so that prolly was a factor in it all.