Drambuie's popularity is largely attributed to the rusty nail cocktail in which it's paired with scotch. The Prohibition-era cocktail took the edge off bootlegged whiskey and helped introduce U.S. drinkers to the newly imported liqueur. The fact that it was a favorite drink of the Rat Pack (Frank Sinatra, Dean Martin, Sammy Davis Jr., etc.) helped propel the rusty nail and Drambuie to the fame they retain today.