At matchpoints, you lead your singleton ♥. Partner plays the Ace, but simultaneously the ♥2 falls out of his hand accidentally. The Director rules that the 2 is a minor penalty card. Partner returns that card and you ruff. as declarer drops the ♥K. From the looks of dummy, a Diamond return looks less dangerous, but do you have to return a Club because you have the information that the ♥2 is not necessarily a suit preference signal?
Benefits include:
Plus... it's free!