I did that once.
This was just before Christmas, I was leaving on vacation that afternoon and I had been at work all night long. I was pissed that I'd have to leave soon, go home and sleep for a while befre hopping in the car for 20 hours.
CIO was on the other end of conf call, and I said "this guy's a fucking douchebag". I thought we were on mute. Once the line went silent, I figured hey, if you're gonna go down, go down in flames. I launched into a tirade on how incompetent he and his staff were, when he attempted to retort I told him I was leaving the office now, and walked out.
I should mention that this guy had been my peer at the acquiring company, and had recently won the CIO slot over me post-merger, so I knew I was probably a dead man walking anyway.
I was shitcanned before I got out the door.