This is the one that hurts. I was at work and had a bad block when talking to a high up manager in the company which I have never met, and he said this. We were discussing a very important topic, so tensions were high. I probably overreacted when I replied, "I have a f\*cking stutter you asshole, let me finish." Luckily, neither of us ended in HR. We have a good working relationship now.