Duke It Out is a rule set that gives you a way to fight basically anything with anything else. It doesn't matter how weird or unlikely the fight it - there's a way to do it, and let the dice proclaim the victor!
Duke It Out is designed for two players, but accomodates as many as you have table space for. Pregenerated templates can be selected that roughly fit the model you want to use for quick play, or you can make your own based on the many examples with just a few minutes thought. It's a great intro to tabletop wargamming for players new to the genre, and experienced players might find it a refereshingly elegant substitute for leviathan rule sets bloated into library shelves of books, supplements, magazines, and downloads.
Give it a look - it's totally free!