Probably every movie with a battle scene where the two sides get involved in hand to hand combat. Doesn't it usually boil down to both the protagonist and antagonist for some reason being the best fighter in each army, slicing their way through hordes of nameless extras until they meet somewhere in the middle of the field for solo combat? Also once engaged in a fight with each other the extras seemigly become content to ignore them and let them have their solo duel.