This happened back when I was in High School. Well, the beauty of the school, which happens to be my classmate, was facing her back against me, and I paid no attention to her. But suddenly a classmate of mine accidentaly bumped into me and I fell forward. Desperate not to fall, I grabbed onto anything. And, what do you you know, I accidentally groped the beauty's behind! She yelped(yup, yelped). Anyway, I still ended up falling face first, and when I got back to my feet, she suddenly slapped me in the face. In front of the class.
Good thing noone was actually looking at me when I fell.