I have one. (I might have touched on it in a previous post.)
I had the hots for this college athlete. She had a big, fit body, really robust, and beautiful skin. I wanted to fuck her from behind so I could hold that perfect ass while thrusting into it.
We got together after a couple of drinks one night. In my room, we stopped to strip down, and the first thing she did was circle my erection with one finger and thumb, and ever so slowly pull toward her until my foreskin closed completely over my glans.
I stood still. First time any girl had done that with me. I had no idea what she was doing but it felt wonderful. My eyelids fluttered.
Then she pushed my skin back all the way to the base, exposing my cockhead fully. As soon as her hand bottomed out against me, she repeated the pull toward her, and once again my foreskin enveloped my glans.
She held it there for a few seconds, tentatively sliding the skin back and forth over the head. I wanted that moment never to end.
She let go and we resumed our foreplay. When I started to go down on her, she pulled me back up and said she wasn't into that. Then she added:
"I can suck on a guy all day, but I don't like him going down on me."
And of course I thought this would be my (extra-)lucky night.
But she made no move toward my cock again. We found a condom and fucked for a good half-hour. I did get her up on her knees for a good doggie-style ramming, which made me cum in her exactly as I'd wanted to. But I never got that "all day" blowjob. Wasn't willing to ask or beg for it, either.
So I think what really happened was, she was testing my cock for foreskin. When she found it, she chose not to put it in her mouth.
I still jerk off over that sensation of her pulling my foreskin.