I'll start:
Alright , this one is not mine personally but its close. The first shop I worked in and learned the trade there was a great shop in Long island, New York, one of the techs there had over 20 years experience and he was one of the best plumbers I ever met. He told me a story he called the "Poseidon Adventures". He and the boss man went on a call in Riverhead, a public building had a major sewer backup. These guys were used to doing 'country plumbing' drain calls (mostly septic tanks) so they proceeded to open a cleanout in the basement, they forgot that this was not a septic tank, it was a city sewer connection....it turns out the entire public sewer was blocked in the street and they neglected to check the man-hole before they opened the cleanout....
The floods of Noah came flying out of that cleanout! They ran out of the room and tried to hold the door against the onslaught of raw sewage...it didn't help, the sewage rushed down the stairs and flooded the entire first floor. I don't know how they managed to clean it all up, but that story will live on in that shop for eternity.