Once I was out on a second date with someone. Met for drinks, hit a movie (more drinks there), a couple more after that, some photobooth opportunities that made me feel the night was going awesomely, then eventually back to her place for a nightcap.
Wasn't too long before things were definitely heating up. Going at it and I realize that she's stopped responding. No more words, no more sounds. I look down and her eyes have rolled back into her head. Being half-drunk and not with any medical training, I attempt to feel for a pulse or breath but can't seem to detect either. Panic cloaks me and I begin to hunt down my phone to make the most awkward 911 call ever, before she starts gasping loudly for air.
A short time later, she explained that she had some heart condition and sometimes things just....stop. Pretty terrifying surprise to find out in that manner. Almost glad that things didn't work out so I wouldn't be subjected to that situation again.