I was working on some Windows Media DRM stuff and would get pinged with the really loopy support emails, most of the time not to have me fix them, just more of a heads-up. One said "WHY THE FUCK ARE YOU ON MY PC EVERY MORNING GET THE FUCK OFF MY COMPUTER". I actually started to reply to this chap to see if I could get some sense, but a VP was nearby and saw my screen. They picked up my keyboard, wrote "FUCK OFF" and hit send.

I'm sorry, but that is kind of hilarious. I was lucky that I rarely had to deal with people like that. Most of the time is was low-level C folks who had found a real bug in one of the tools, compilers, etc.