Barker

noun

1. Someone or something who barks.

   "My neighbor's dog is a constant barker that keeps me awake at night."

2. A person employed to solicit customers by calling out to passersby, e.g. at a carnival.

   "Bob had amassed a considerable stockpile of double entendres from his days working as a barker for a strip joint."

3. A shelf-talker.
4. A video game mode where the action is demonstrated to entice someone to play the game.

   "The barker mode of the arcade video game convinced the teenager to spend a quarter."

5. A pistol.