While “The Walking Dead” may rule basic cable, “Dexter” singlehandedly made Showtime a contender in the world of premium packages (and with good reason). The show’s first season was fresh, exciting and, quite often, darkly funny.  The premise of a serial killer who only murders killers wasn’t exactly new (the completely atrocious “Suspect Zero” did it in the worst way possible), however “Dexter” was unique in that the audience sympathized with and frankly, flat-out liked this violent psychopath.  Add in a talented supporting cast and some genuinely effective plot twists and you are left with the best new show of 2006.