Two that have happened to me:
I Just Had Sex... in the middle of it, full volume. We had to stop for a bit from laughing too hard. Don't know what the people in the rooms around us thought.
Just now-- Almost Lover when I was speaking to my ex. Still feelings between us and it was a very intense awkward cause we both could see the other was thinking about it. There was a bumbling forehead kiss that was really both of us were thinking about kissing each other, and he left before the song finished. XD
Tell me yours?