John Wayne, who kicked ass in numerous movies but who did his best work with one director, John Ford, vs. Toshiro Mifune, who kicked ass in numerous movies but who did his best work with one director, Akira Kurosawa. The battle is not between the actual men but between the personas they embodied onscreen: which cinematic bad-ass will emerge victorious?
To make this a fair fight, this will be a fight without weapons (since with weapons, Duke's rifle will probably beat Toshiro's sword -- though Toshiro would make it close).
And speaking of Mifune at his bad-ass-ed-est, Criterion has announced A three-disc special edition of Seven Samurai for this September. New special editions of Yojimbo and Sanjuro will probably follow soon after.