My (technically) worst teacher was also my best, i won't name him but in his glorious career, he usually taught from word of mouth, because he enjoyed eating the chalk and then never had any for the blackboard. (sometimes he sent pupils next door to borrow some, only to absentmindedly eat it again)

He sang from an upside down hymn-book, scored a try (rugby) himself after getting exasperated with us for not scoring, and got frogmarched off the pitch, would regularly stand upside down in the corner of the room while allowing us to chat as long as we weren't too loud (part of his health routine), and sadly got fired after bringing in a samurai sword into class to liven up our history class.

It sounds strange by anyone's standards that he'd have been hired, but he had been at the school a very long time and had been known for his eccentricity, so i presume my class got him around the time he really went off his rocker.