Been playing a lot of Skyrim (Dragonborn) but as awesome as it is it gets to be a little "rinse-and-repeat", even with the level 81 cap which forces you to modify play styles to keep leveling it gets to be a lot. So I started looking into mods and after reading tons of reviews I installed "Companion Vilja" and while her quest line is not particularly special she is an amazingly robust character. I mean thousands of lines of dialogue from simple comments about an innkeeper in Markarth to more thoughtful monologues on the nature of love and loss. She is easily the most interesting character in the vanilla game and makes all other vanilla game companions and Carls seem annoyingly mundane by comparison. It's truly amazing that a couple of unpaid modders would put so much time into creating something like this but bravo to them because they made the game far more interesting.
This was one of the mods I installed when I went PC, and I concur - excellent.
Also downloaded a mod that really beefs up your player home (the Lakewood one) - becomes almost a small village. A few other assorted mods (dungeons/etc), and a self imposed "get all Dragon Priest masks" quest, and there's another 100 hours out of this thing.
Amazing game.