I have a few times, not really what people think of when you say 'cry' but yes I've had tears run down my face.
Sometimes an orgasm is an incredibly overwhelming feeling - typically when I have multiples or one prolonged orgasm in a short period of time. Basically the stars have aligned, my body can't stop tingling and I start to giggle (gotta love endorphins

), suddenly my eyes just tear up and I'm laughing and crying at once.
It's a damn good feeling and I wish I was able to reach that level of pleasure more often.