My favorite incident remains the “Internet goes down every day at 4pm”. The office was complaining so we investigated and looked at the logs and sure enough, the switch to the office was dropping off every day at 4 and coming back online about 15-20minutes later. We trouble shot the thing and couldn’t find out what was wrong, so we swapped in a new switch and the very next day, it went down again. We headed down there to see what the hell was going on and thats when we figured it out. Every afternoon at 4, the cleaning guy unplugged the switch to plug in his vacuum, did his job and plugged the switch back in when he left.