Mine was when my manager and boss sat me down to tell me that after working 72 hours a week with no lunch breaks, travelling 3 hours a day to work, and having to take on all tasks because we were understaffed that I was incredibly lazy and I had to do more. They then told me that they thought that it would be best if I broke up with my partner of almost 5 years, move out of our flat and to move near work so that I could spend all of mine time working there with no distractions.
They of course were very shocked when I quit 2 days later by text.