Vigilantes

Vigilantes are daggers. They have a 5% chance of inflicting the Stop debuff onto targets when wielded by Noctis or Ignis.

Source
Vigilantes can be found as a collectable in the Glacial Grotto maze during Chapter 15. They can be sold to shops for 7,500 gil.

Trivia

 * There are many weapons throughout the Final Fantasy series called Vigilantes. However, it is more often the name of greatswords than daggers.