I slapped the hood of a car once--quite hard, which was turning left right into my kids, who were biking with me to the library (this was a good 5 years ago). She wasn't looking at us, just at the cars to see if the coast was clear. She stopped immediately. I yelled, "Do you want to kill my kids?" Then she hung her head in her lap. She was upset at what she did.

Looking back on it I can laugh it off, but I was shaken by this then for a good week or two.