So I am currently re-watching the entirety of the the series and something that I have noticed is that there a quite a number of characters that die in the same fashion to the last person they killed on-screen.
Bellow are just some of the examples that I can think of right now.
Ned Stark - He beheads a deserter in the first episode and I believe that this is the last person he kills on-screen. I know that he kills Lady out of mercy after that, but we're mostly counting human characters. He is later beheaded himself.
Catelyn Stark - Cuts the throat of one of Frey's daughters before having hers cut seconds later.
Roose Bolton - Last person he kills on-screen is Robb Stark by stabbing him in the chest, and is later stabbed in the chest himself by his son Ramsey.
I'm sure that there are plenty others, and I would really like to know them so let me know if you can think of any more.