With a title like that and my all-around queasiness about blood in general - and anything bad happening with male packages in particular - it was a pretty big longshot I would even open the thread. But here I am.
I'm not sure this tops it but - ALERT! - DON'T READ THIS IF YOU ARE QUEASY LIKE ME - I DON'T EVEN WANT TO READ IT MYSELF BUT IT'S ALREADY IN MY HEAD NOW SO I MIGHT AS WELL TYPE IT OUT - I once had a situation where I began to bleed out of my penis during sex. I was receiving oral and looked down and she had blood in her mouth. Not just a tiny little hey what's that? trickle of blood - a mouthful of blood.
Did I vomit? Yes, I sure did.
I ended up going to the doctor and he kind of shrugged and sent me for a cystoscopy (like a colonoscopy except up the sheboinker). They didn't find anything. He decided it must have just been a random freakish rupturing of a random blood vessel due to the random vigorous pressures that were taking place at the time.
I went about 2 weeks with no sexual activity - then eased back into it. There was no problem and things gradually got back to previous levels of vigor. That was ~25 years ago and I have never had a problem of the sort since.
Fucking gross experience though.