Mine is that I can't stand bullshit and bullshitters. More than once, in my youth, when I was even grumpier (would you believe it), I have told interviewers who came across as full of shit (as most morons are) to fuck themselves and walked away. I did it with clients too.

I encourage all people with brains and self respect to do the same. Nothing bad is going to happen. Most people will admire you for it, and it won't hurt your career or progression in business or academia a bit. People who feel the need to behave like arrogant assholes rarely count, or they wouldn't have to do that to feel better about themselves, and therefore they cannot do anything about it other than take a long sad look in the mirror.