Well, there was one night when I accidentally had three girls in my bed. Had sex, but not a threesome. Sorry for the length, but the story is in the setup.
I went to a club one night last summer, with the intention of just hanging out and having a good time. I've found that going out with the goal of meeting women is what usually leads to a disappointing night (most guys never seem to figure this out), so I just go to hang out and have fun, and if I meet anyone it's just a bonus.
My buddy that I was hanging out with started talking to one girl for a while, and they seemed pretty into each other. Good for him, right? But I didn't want to be in the way so I let them be and gave them space. A little while later he finds me again and asks if I can wing for him. Like a good friend, I say yes without even seeing the other girl. I turned out there were actually three of them in the group, so he wanted me to field the two of them for a while. Not as much a winging situation as it was just defense against cockblocking. Cool. I was getting bored anyway.
It's pretty hard to keep the attention of two women simultaneously in a club when other guys keep coming up to try to talk to them. I wasn't offended or anything, I mean, as long as they're occupied my buddy has a better chance with his girl. They eventually left my table with a couple other guys to dance, and I was actually a little relieved. I was a little tired and thinking about leaving (they were younger and the conversation wasn't really very interesting).
A few minutes later when I went up to the bar to get one last drink, my buddy found me and filed me in on his plan. Apparently all three girls were ready to go, since things were going well with him and the one he was talking to, while the other two were fed up with the other guys for being handsy. They refused to split up the group, but were fine with him and her hooking up if they had a place to crash for the night as well. That's where he needed me - my apartment was bigger and closer.
So, we all end up at my apartment, with the plan for one to sleep on my couch, one to sleep on the other side of my king size bed, and the other to sleep with my buddy in my spare bedroom.
Shortly after we all retire to our sleeping areas, the girl in my bed suddenly and without warning gets frisky, so we proceed to have a quick drunken session of fun and then pass out. Because why not, right? I was glad to not be the "Sexless Innkeeper" for the night. About an hour later my buddy knocks on the door and tells me he struck out because he came on too strong, and he has to leave since he has work in the morning. As soon as he leaves, the girl he was talking to all night just comes in and crawls between me and the other girl. Whatever, I'm just trying to sleep at this point. I woke a little later to because she was giving me a blowjob while the first girl was still sleeping. About an hour later I woke up again and the third girl was crawling into bed on my other side, briefly explaining that she was lonely in the living room. She and I ended up making out and doing hand stuff while the others slept. There's no possible way in my life all this could ever happen if I'd tried to plan it.
In the morning when I woke up, I was on my back with my arms around them and different girl's boobs in each hand. I got up and took a shower, made coffee for everyone, and then we all went out for brunch before I took them all home.
My buddy later asked me if I thought he still had a chance with the girl since he was apparently pretty smitten, but I didn't have the heart to tell him.
Since it was all too good to be true, I went and got tested the following week. Glad to say I was still clean after a very dirty night.
TL;DR: Nice guys don't always finish last; sometimes they finish three times.