Yes, yes I have ... I made one of my few life rules then, too, it goes as follows:
"When you find yourself regularly sitting at your desk and fantasizing about walking into said job with a fully loaded automatic weapon, and using aforementioned weapon to obliterate every fucking mutherfucking son of a bitching asshole at work, then is it time to start mailing out resumes pronto."
Seriously, that's my personal dealbreaker. When I start thinking I can justify homicide on the job, it's time for a new job.