War films mostly.
I also loath the injecting of modern themes and concepts into historical/war films where they have no place.
Someone near the OP mentioned Spartacus, that's one that really gets my back up turning a rebelling into a soap box for the film makers to whine about subjects that no slave army of the time would give a damn about. For war films, turning one war into another to whine on about it, see The Thin Red Line and MASH turning WWII and Korea into Vietnam.
OT: Most medieval battles are unrealistic, to my knowledge it was mostly two formations trying to break each other, not everyone breaking off to fight individually.
Battles would devolve into a melee, even ones heavily using pikemen. The main issue I have with the medias portrayal of medieval battles is that it wasn't actually one on one combat and those fighting, especially dismounted knights would break off into pairs with each covering the others back as they tried to find and attack those who were vulnerable (like those lost and confused in the fighting, especially those who lost their companion).
Along with that is the portrayal of the High Middle Ages and it's glamorous plate armour without the use of the weaponry used at the time because swords = cool. Not every bloody knight used one and those that did were using greatswords by that time for their greater weight and shock value, not for their cutting or piercing ability.
They mixed in plenty of short, fat hacking swords, maces, warhammers, militarized picks and axes which were more damaging and easier to handle in combat.
I'd rather have a flanged mace or shortened lucerne or bec de corbin hammer with their flexibility and speed if I encountered someone in armour.