This is from a job I've quit many, many years ago.
public enum OurBoolean
If I had had access to George Boole's coffin back then, I could have used it to generate electricity from his spinning corpse.
It was actually named a bit differently. I've replaced the company name with "Our".
So I asked the father of this hideous child why in the Malebolge did he code it like that. His answer was "dude, it's logic!"
You see, in propositional logic there are those propositions which are always true (tautologies), those that are always false (contradictions), and those that may either be true or false (contingencies). The "Unknown" value in the enumeration was written so as to represent a contingency. Nevermind that everywhere in the application, this enumeration was used instead of your regular, day-to-day boolean variables. There was also a considerable amount of code to convert from the enumeration to normal booleans. The part dealing with "Unknown" was full of //TODO comments.
As for the null value, that was put there so as "to comply with the DBMS". Which is why they made me look at this thing in the first place, they were having troubles with null values when they came from a database. I tried my best at explaining to them why a null reference and OurBoolean.Null were not the same thing. But the dev behind the monstruosity kept saying "but it's written 'null' in there, so it has to be null".
That hideousness is what keeps you and I [sic] employed!