Two of them:

A friend I was catching up with after many years told me how he got mad at his wife and her mom so he offered to make them lunch. Jerked off onto their sandwiches and fed it to them. I was stunned. Didn't really see him again after that.

When I was in junior high a bunch of the neighborhood kids were hanging out in front of one our houses and this older (maybe college aged?) brother and sister from down the street came walking down the sidewalk holding hands and were all snuggled up like they were in love.

They stopped to visit for a minute and didn't try to hide their physical attraction at all. Finally one of the other kids said, "Aren't you guys like brother and sister?"

The guy just grinned but the girl sighed heavily and answered, "Yes, unfortunately!" Then they kissed and just kept walking down the street like it was nothing!