Mike Judge made a stupid little one-minute cartoon for SNL one year about a loser wanting his stapler.
Years later he thought it would make a great premise for a feature-length film. The result was Office Space, which I'm betting ranks pretty high on everyone's favorite movie list.
My point? Sometimes a razor-thin premise can be a great starting point for a good story or movie. I almost think, if this isn't some joke, that Joust might actually make for a decent post-apocalyptic movie idea.