I like shows where you literally don't know what will happen or who will be spared and leave you having to pick up your jaw from the floor.
But I don't know if you can top the Red Wedding or Hector and "ding ding ding ding....boom!"
BB and GoT are easily the best written shows on TV. The Walking Dead is close, IMO but it has its lulls.
I haven't watched Justified but I've heard good things...but I have a 4 year old and, next week, a newborn so...no more new shows for me, just don't have the time. If I did though, The Americans is next.