Middle-earth: Shadow of Mordor’s best feature was easily the nemesis system, and an upcoming mod seeks to add it to Skyrim.
If you’re unfamiliar with Nemesis system, it works like this: enemies will remember the players actions, such as whether you had previously killed them or been killed by them, allowing them to move up and down the hierarchy. Get beat by a grunt often enough and it could work their way up the ladder, and they will bully you for constantly dying too. And now modder Syclonix seeks to add a similar system to Skyrim (thanks PCGamesN).
Syclonix calls the in-development mod Shadow of Skyrim: Nemesis and Alternative Death System, or SOS-NADS for short, as they described on Reddit. The post paints a pretty picture of how they imagine the mod to work narratively, telling a tale of a player bested by a bog vampire called “Breaks-Many-Shields.”