Granted, I work for a very small company and, as the bookkeeper, I pretty much have to "deal" with everyone in one way or another, so it was somewhat pointless to proclaim I was not going to do so any more. But it was a nice 2 weeks while it lasted.
When my boss came to my office a few minutes later I started to apologize (to my boss, for causing a scene, never will I apologize to that salesman) and he actually said I had nothing to apologize for! In fact, the invoice I.S. (Idiot Salesperson) had originally come to me for was approved to wait a day just out of spite. I love my boss. It's tough, sometimes: I certainly don't want to go out of my way to help or clean up after I.S. but most of the time it's in service of keeping the company from looking bad, I.S. just gets to ride on the coattails of my over-riding work-ethic.
(and, no, this wasn't the first time I.S. engaged in rapid-fire double-talk after ignore rules that were made in attempt to keep him in line in the first place... it's a long, convoluted story with him)