Scabbard Strike

 
Prerequisite(s): Combat Reflexes, Stunning Fist or Stunning Attack
 
Benefit: Once per combat you can surprise an opponent with an unexpected blow from your scabbard. Make a normal attack roll. If successful, you deal subdual damage equal to your unarmed damage and your opponents is forced to make a Fortitude save (DC 10 + Class Level + Wis modifier), or be stunned per Stunning Fist or a monk’s stunning attack. Scabbard Strike can only be used with a scabbarded weapon of at least medium size and only with the scabbards that are worn on the waist or loosely slung. Scabbard Strike counts as one daily use of the stunning ability.
 
Source: Mongoose Ultimate Feats