Cult of the Wind
In Cult of the Wind, players compete and cooperate in ritualistic multi-player human dogfights, complete with imaginary weapons, pretend explosions, and airplane noises made with their mouths. Shower your friends in a hail of imaginary bullets and proclaim, "I got you! You have to lie down," to which they respond, "Nuh-uh, I have a shield." You argue about whether or not airplanes can have shields, meanwhile some other guy does a cannonball onto your head while whistling. It's great.
With an intuitive point-and-click level editor you'll be able to craft new levels or modify existing ones, then immediately share them with anyone on a server, even if you aren't the host. You can also craft a personalized appearance for your character with numerous articles of clothing and more.