New Vegas Killer, of course! Bobby Bass is a very well written character and he has an amazing voice acting. Judge by yourself:
"I talk about a few things: killing people, plants, dogs, and tittites. If you branch beyond that, odds are I won't give a fuck."
In short, a very normal person...

My opinion is: New Vegas Bounties (all three chapters)

I really enjoyed ''For the Enclave'' New vegas mod, though in all honesty i've not played many story mods

I’d say that The Someguy Series is one of the best set of quest mods in modding. It is on par with vanillla writing and even goes above it at times. Really, go check Someguy2000’s channel. He is funny as hell and has a great fan base, but try to pay attention when he talks about things like mythology, history, film, and writing in general. This guy is really intelligent despite his what he says about himself(which is just apart of his comedic dialect).

I’m gonna go against the grain and say that Crossroads is one of best written mods for New Vegas. Really check out this mod. Al did a review of it already, but he only scratched the surface. This mod goes really in depth with the vanilla game. The mod author himself said that this mod requires at least 10 playthroughs to fully get everything out of it. The mod is meant to be played along a actual playthrough and the companions you get has a lot to say about the Mojave and can even effect vanilla quests(I am not kidding). The mod author behind this mod is also working on the slave prison quest for the Frontier mod. I’ve seen some gameplay of it, and it goes beyond vanilla writing and design in my opinion. The shit you can do in that specific quest line is crazy. Seriously, give Crossroads a try and give the mod author some love.

the bounties series rocks... that and a world of pain are the best mods ever.

The series by someguy2000 is absolutely amazing and I've heard that autumn leaves is good but I've yet to play it. Project brazil at least from what we've gotten so far was also amazing. Lastly though I'd say tales from the commenwealth fits in seamlessly.

someguy2000's mods, Beyond Boulder

I've always been a fan of both bounties mods. I can replay those again and again. The new atomguard mod for FO4 is pretty good as well.

bounties series in FNV, The voice acting is the best of all the quests mod i ever played.

Someguy2000's work, Fallout New California (previously known as Project Brazil), and The Frontier based on the footage released.

The Someguy series. Easily.
I love them all, but I think of all of them, the inheritance doesn't get the admiration it deserves. There are two, expertly written things in this mod, that just, really deserve it.
First off, is Bradley. He's a rough merc who happens to have a dad who made a difficult choice. He despises him for it, and what that choice meant to him. He's had a hard life, and he's not a good man, but he has a real opportunity here to find something that will change his life. He'll no longer be a merc, taking jobs until he inevitably takes a bullet or makes the wrong deal. He has a chance because of his father to become something, and we learn his story throughout the mod, and empathise with him, bond with him. He's not a good man, like any of Someguys characters, but he's an honest, even human character, who has something to drive him. Then, when we see his death, either killed at your hands in a desperate bid for survival, or taking his life in the hopes you will avenge him, we see his life ended, completely beyond our control, because of the thing he was after. And knowing that, had we as the player never delivered that package, or convinced him to follow it to it's end, he would still be alive, makes it all the more personal. It's a tragic, pointless, and even pathetic end, and it makes the ultimate outcome of the story matter so much more.
Then, there is Zimmer. The head of the Syndicate in the Mojave, and slightly obsessed with the Courier. Playing this after Bounties I, we learn that Zimmer operates in the same organisation as The Judge, and is aware of the Courier's part in ending him. Zimmer explains something that I really think resonated with me, despite being relatively simple in nature: anyone can die. But it's the way he says it. It jives so well with the world of Fallout, and it puts a lot into perspective. That all it takes is one person to catch you at a bad time, when your drunk or high, and they can kill you then and there, is really pretty poignant, because it was exactly how Bradley got killed. It was exactly how the Courier almost died, ambushed and captured, then shot. He explains that he wishes the Courier to die with dignity at his hands, so he can become a legend, the man who killed Courier 6. He then challenges you, one on one, to a battle with the Katana, a lost art from a more civilised time, in a final battle, with the only hindrance being the games poor melee mechanics. His death then evokes the wrath of the mystery employer, who Zimmer refuses to refer to by name. In his letter he states that the player has killed the one man he ever considered as a son...
Not to even touch on the Inheritance itself. Pre-war gold, the inheritance of Old-America, the Inheritance of guilt, the retribution coming the Courier's way for his acts in Bounties, killing Judge Richter, or more simply, Bradley's inheritance from his father. It's intelligent writing, almost serial in nature. It's a story told on the arc of a larger story, and one that makes full use of the games story telling abilities. It has everything a modern tragedy should, and it's not too much geared in one direction, combat or dialogue, there's a good split of each and yields a variety of gameplay options for different players.

Truly, the best written mod, IMO.