Used to live by an area with a 'caution falling cows'[1] sign. Was never there longer than a few hours before being stolen again. Sure, you can buy them, but I guess it's not the same?
Never did see it more than a handful of times over many trips/years.
There is a freight train grade crossing nearby, and there is an official sign which reads "NO TRAIN HORN" and then below it, there is very meticulous lettering reading "EXCEPT SOMETIMES" and I swear I have never quite figured out whether it is official, or some joker's joke that's been permitted to stay there for years on end.