Deadly Slinger

Your skill with a sling is lethal to your enemies. 

Prerequisites: Dex 15, Deadly Aim, Weapon Focus (sling or halfling sling-staff), base attack bonus +3.

Benefit: Whenever you use lead (or metal) sling bullets, you ignore the penalty on ranged attack rolls from the Deadly Aim feat. You also gain a +2 bonus to checks made to confirm critical hits with your sling attacks. 

*This feat benefits users of the sling or halfling staff-sling, and is the original concept of Weirdo and Xunal on the Homebrew thread of the Paizo RPG website. (Xunal; Deadly Sling feat)