My favorite faction would have to be the NCR, even though I always betray them in the end. They are as close to a real government that the old world had, and that is what needs to be done, not some dictator with no real succession system in place. Then again, as long as I have my Imperial New Vegas, I'm good.

NCR cause they're not so crazy as fuck like the others

It would probably be the D.C. Brotherhood of Steel. I really like Elder Lyons he is a really good leader who really cares for the people as opposed to many factions who'd be more than willing to stab you in the back.

The Legion.Why you might ask,let me tell you why.The Legion was the first faction i completed Fallout with,also they are brutal i love being brutal so i love to be in the Legion to devour and destroy.Also i kileed Ceaser because he annoyed me i liked more Legate Lanius to be on his place also i choose to kill many people and devour them i like that also i killed Mr.House im a cannibal too in the game so i see no reason why NOT to join the Legion even if i joined them once i still go with the NCR though but its been to loong i might join them again.

Must be the Talon Company (guess it must be FOOK2 wich made them my favorite) but I think they are just awsome,they walk around DC,smoke,scream "Talon Company!!!!",have a big arsenal of guns and the best thing is their armor,I felt just like this as I saw them for the first time

Spoiler:

I'm gonna go with NCR just because I am a military guy myself.  Also they seem to be the only people genuinely trying to restore humanity to what it once was. Plus ranger armor is one of my favorites.

NCR i like the military group who mows down the crazy savages of the legion

Even though I side with no one in FNV I do like NCR, military style is what I like. Guns, commanders, Boone, first recon. Ah, I know only a little about them but they're already my favorite!

No one really.

In 3 I liked Lyons' Brotherhood, I suppose.

I'm now playing FNV and it's kind of muddy. For the most part I like the NCR(rangers mostly) and flag, but I don't like their greedy expansionism. The Legion was a loss from the onset. I'll never get behind that failed and outdated mindset on civilization. slaves and conquest? next. Haven't met the boomers yet, but I see people mentioning them. The Khans are alright, but nothing to write home about. House? Nah. I'll be going for the independent route. Enclave. nope.
What other factions are there, really?

My favorite fraction is the NCR, because of how they are pretty much the only thing that close enough resemble the military.

I always liked the Brotherhood of steel. they just look awesome in their power armour and always seemed like a faction to be contended with.

as an "old" fallout player I can't not stand for the NCR! (although the end of goodsprings sucked a lot!!!)

I do enjoy BOS, but I like the outcast a little bit more from FO3. The black and red armour looks a hell of a lot more badass.

I have always been a fan of Caesar's Legion...wasn't the biggest fan of the members that were in the game as it was just the military. But all the various bits of dialogue and lore about them really intrigues on what their actual territory and homes are like.

They might not be an actual faction but I always liked The Kings from FONV. I don't know why but they look like a pretty chill group. As for an actual faction I really like The Followers of the Apocalypse because they're the only ones who look like they actually care for the betterment of the human race. Here's to hoping FO4 will add a Super Mutant faction!

Ncr... and i don't know why... new vegas have such an amazing lore.

My Favorite faction is the Enclave in my opinion they have been superior over all the other factions they have Adams Air force Base with a huge carrier, if the Lone Wanderer wasn't with the Brotherhood they probably would of pushed the Brotherhood back and took over the citadel. They even survive in Nevada where people think there is no Enclave. But there still living in secrecy, they are truly a government that can stay strong

Brotherhood of Steel, big ass energy weapons, badass heavy armors, and yea a big freaking robot who throws nukes at you, how can u beat that?

Embrace democracy or you will be eradicated!

Brotherhood of steel for sure, although i prefer the Brotherhood in fallout 3 over them in fallout new vegas.

My favorite faction is from Fallout is "The Omertas." I personally loved how intimidating they were, and their Goodfellas-esque nicknames. With the Vegas setting, I think it really called for a mob angle - and this delivered. I just wish they were expanded on a little bit. Once you explore the Gomorrah a few times over, you realize they don't have much content (beyond a hotel and a side quest). It's a cryin' shame because they really are an intriguing and fascinating group.