Two-player-only game (only works over wifi). An imaginary sword extends from the front of your phone. Your phones track where the swords would be and emit a "clink" sound when the swords hit.
Open Source. Revenue from sales is distributed between people who contribute patches. See http://opensourcetown.com/projects/sword
Market link: com.opensourcetown.asword
Web site: http://opensourcetown.com
Market downloads: 1,000-5,000
Market rating: 1.9 / 5.0