An amazing amount of NPCs had their dialog fully written but were later removed from the game. This list is probably not even complete.
Jess Heinig recalls:
There were originally going to be two other raider tribes in addition to the Khansthe Vipers and some other group whose name escapes me. We had this idea worked out for the Vipers being in a cleft in a canyon with some beat-up wagons or motor homes, and a sort of snake-worship-cult thing going on. There was gonna be a quest where you could become an honorary Viper and go through their pit of serpents and gain the Snakeater perk for free. Sadly, we just didn't have time to actually build the map.
Some of the Blades shared a common message file, so I list them in one line.
Other named members of the Blades, but without a message file of their own, are Books, Scars, Gunner, Twitch and Hammer.
The Rippers were scrapped completely. Originally, they inhabited the building later unconvincingly turned into a deathclaw lair, and were constantly fighting the Blades. Their leader was Tangler, to become a Blade you had to kill him and bring back his hand as proof. According to Nicole, Morpheus used to be a ripper. This dialog line can't be accessed in the game any more.
Most cathedral NPCs give you only a small part of their dialog. A good example is Viola, who has many lines that cannot be accessed. So it's hard to tell if actually any NPCs were completely removed.
They may have been supposed for the Military Base or the Master's Lair, it's not always quite sure.
There are some MSG files for a type of random encounter that was never fully implemented: people from a nearby location who had lots of dialog, depending on your rep there, could give you news or lead you to their base.