The worst insult I distinctly remember is when I was studying in England a few years ago.
It was my first time riding a bike on the road with cars, OK. I remember I was on the left side of the road trying to turn to the right side but there were many cars behind me. I hesitated a few times whether I should turn - All of a sudden a car drove next to me, with a lady scrolling down the window (she was not the driver) and yelled: "What do you think you are doing you silly cow??" and disappeared from my sight.
Gee - I knew I was a silly cow but I didn't even have the time to say "F*** you bitch" back to her.