The Iron Tavern and I have to say, it looks pretty awesome. I haven't had the chance to look at the rules yet, but, from the review, the game is all about speedy resolution so you can keep things moving (you only use a d20!).
The best part? It's completely free. I'll definitely be adding this to my ever-expanding collection of games. Even if I never play it, I'm sure that some of the 170 page rulebook (only 10 of which are actual rules) will be useful as source material.
This game has actually been around for a few years and was released under the creative commons license. That means you can take the work of German designer Christian Kennig and mold it to suit your needs. Several variants already exist, including options for modern day zombie-killing and Mutant Future weirdness, albeit in German. I'm sure as this product gains steam over here, we'll see those options, and many more, make their way into translation.Check it out here.