Your precision with the staff-sling is unmatched.
Prerequisite: Str 13, Weapon Focus (halfling staff-sling).
Benefit: Whenever you use lead (or metal) sling bullets, you add your Strength bonus to your sling damage.
*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; Power Slinging feat)