In this scene from season 7 episode 6 of Entourage entitled "Hair" Turtle tries to convert Johnny Drama to the new brand of tequila he is promoting. Drama makes it very clear that he plans to stick to his Blue Label.
There was also a very brief Glenrothes sighting in this episode. Only someone with a well-trained eye would spot it. Here's another shot of the Johnnie Walker bottle from later in the episode.
Let's not forget this Johnnie Walker ad Kevin Dillon made a few years back.