MMObility: Real-life location games for your daily walks

I've been having a lot of fun with Parallel Kingdom lately. It's a location-based MMO brought to us by PerBlue, one that offers a layer of reality thanks to the fact that it is built on top of the real-world map. You can claim your real-life block, help other members of your city, and trade with other players from all over the world. It's actually a pretty simple design, but it helps to give the game a sense of realism.