Impact Shot

The force of your sling attacks can push the target backwards. 

Prerequisite: Weapon Focus (sling or halfling sling-staff), base attack bonus +6.

Benefit: The critical multiplier of your sling increases to x3. In addition, when you confirm a critical hit with your sling, the target is pushed back 5 feet. 

*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. (*Weirdo; Impact Sling feat)