One Shot in the Dark

From the publisher: One Shot in the Dark is a rules-ultra-light, classic-style fantasy RPG that can be played solo or with up to 4 people. It's a pick-up-and-play game that requires zero prep. It's also a true one-shot in the sense that it can be played in full in a single session, usually in less time than it takes to watch a movie. A standard deck of playing cards and a set of polyhedral dice (or a dice rolling app) are required for play.