I have a couple. In my last job, I was transfered to a new school. The principal set me up with the girl who was doing my job in a temporary capacity. She was to share with me her caseload and get me trained in the frame of a two hour meeting in her pathetic little office.
Well, by this point, I was thoroughly disguisted by the conservative small town mentality and exhausted by my job as a special education teacher. I let slip my true feelings on some procedures I found to be rigid and contrary to policy. I also shared a funny little story about the principal's son. He was quite the little shithead.
At the end of our meeting, she smiled warmly and told me she couldn't wait to work together. I got an email the next day from the Director of Education. The little cunt had gone straight to the bitch of a principal and ratted me out. The principal, instead of coming to me, went straight to her superior instead.
I took the opportunity to resign because I was contemplating doing so anyway. That principal had an evil reputation, none of the teachers liked her. I'm happy I did and I'm much better off. Sometimes you need to be betrayed to realize where you're really at in life.