I'm going to offer a confession: When I first read about the Nemesis System in Middle-earth: Shadows of Mordor, I was unimpressed. I could not wrap my mind around how it could possibly work in a way that was both compelling and something that resembled what they were selling in those early previews.
In the end though, they managed to pull it off. Maybe it's not perfect, but it's one of the closest thing to a brand new gameplay mechanic we've seen in a long long time.
In today's new trailer, inspired by the fans, Talion monologues, then unheadenates a very unlucky orc. So it's basically the game itself in a minute-and-a-half long nutshell.