Capcom was the undisputed king of the brawler in the 90s. Their CPS arcade system offered the best of co-op beat-'em-ups, from Aliens vs. Predator to Dungeons & Dragons. Knights of the Round was a fairly early effort from '91, based on the rich mythos of the legend of King Arthur. Lancelot, Percival, and Arthur himself took on a legion of enemies, growing in power and strength (and progressively ornate armor) with each defeated foe. It's a fantastic, fast paced example of the genre.