For perfect projectile possibilities, get your crochet on. Materials are cheap, the pattern is relatively easy, and you can stuff it with anything. I am thinking about plastic beads for this purpose. The surrounding pictures are some of my first attempts. If you wanna give this a shot, check out youtube on crocheting amigurumi crochet balls, they have lots of good technique tips. My only caution is that I have not yet let anyone hit me with one and so until then I cannot officially recommend them as projectiles... I just think that this is going in a good direction. And it ain't girly... especially if you're making projectiles.