Why we picked it: The 2-player card combat of Kongai mashes so many ideas together, it's a miracle that it's a playable game at all, let alone one of the best free multiplayer games on the web. Superstar game-design analyst David Sirlin built Kongai on a simplified skeleton of the Pokemon battle system, incorporating several new layers of interlocking strengths and weaknesses, as well as a strong emphasis on mind games. It's a great game, but what makes it a revolution is the way you collect your warrior and item cards by completing challenges in the other games posted on Kongregate. By helping to bring attention to the efforts of amateur designers, Kongai sets a new standard for community-oriented gaming.
You can play Kongai here.