I've done it twice. Once when a co-worker was constantly critizing our boss, and constantly spending her work time looking online for another job - leaving me to do the bulk of the work. This had gone on for several weeks. She started going on again about our boss, and I told her to friggin' grow up, to go get another job if that's what she wanted, and to quit polluting the place for the rest of us. Then I glanced up and seen a customer had come in and sat down (optometrist office), and I'm sure he heard every word. :oops:
The 2nd was at my last job, and another employee, 2nd in charge, friend of the boss, was always a jerk. He was basically a nice guy though, just always bitched about everything. One day he directed it at me, over something not my doing. And I went off on him. Told him to either treat me with respect or never to speak again to me. I had put up with it for so long, as I was half afraid of losing my job as he was boss's friend, etc. Next morning said co-worker apologized to me, also said he'd told his wife about my going off on him, and that she agreed with me! We kind of almost became friends after that. :-)
Usually though, I do try to put up with things, or try to get them dealt with in a clean way. I try to act professional. But some people just make it real difficult.
:-)