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The nickname "Mr. Ass" refers to Billy Gunn's signature finishing move, the "Ass Pound," which involves him driving his opponent face-first into the mat with a powerful hip attack. As a member of the popular tag team "The New Age Outlaws," Gunn gained a reputation for his charismatic personality, impressive in-ring skills, and entertaining catchphrases, contributing to his status as a beloved figure in the world of professional wrestling.