The sling community is chomping at the bit to design a sling sport that will allow us to sling at the best target ever... other slingers. The central problem has always been the scarcity of slingers. To quote a another member of slinging.org's forums, "I have never seen more than ten slingers together at one time, and when I do, nine of them are beginners." If slinging ever gets a bit more mainstream, our secondary problem will be what projectile to use. I have slung uncut tennis balls at people but unless you're fifty yards away... it hurts. Every projectile with enough weight to make it worth slinging would be injurious, and anything that would not be injurious is too light weight to bother with... so what to do. It seems to me we need a projectile that absorbs much of it's own impact. My first idea is this tennis ball. I have cut it along two dimensions to allow for severe shape distortion on impact but. It still hurts, and it's not very stable, they fall apart after a few hard impacts, the cut continues to grow and I think they wouldn't last long. So the search continues. Maybe eggs?