Under the Broken Moon is an RPG based on the Thundarr the Barbarian cartoon series. The game uses a mechanic where you roll a number of dice equal to your trait score and sum the results.
Thundarr
Mass Combat Rules For Role Playing Games
The Wrath of Zombies blog has a set of free RPG rules for Mass Combat. While written for the author’s own Thundarr style game, they are applicable to a wide variety of rules and settings.