Mr. House.
It's basically Indy Vegas + Greatest Genius in Post-Apocalyptia.
This.
To be more specific I also like the idea of the Follower's of the Apocalypse gaining a lot of power in House's New Vegas and helping the Great Khans establish an empire to the north.
I find that to be the best ending because House will have a mighty empire watching his back (they would be on very good terms due to the FotA having so much influence in both empires) and the NCR as an ally, making his empire perfectly safe from the Legion and the NCR if they ever considered betraying him.