Basically what the topic says. The Courier was never awoken by Victor because the Great Khans spotted him after returning to the grave to dispose of some evidence. Benny killed Mr. House when he returns to New Vegas with the Platinum Chip (He tells House that the Courier haddied, and he had witnessed the scene, but that luckilt Benny had recovered the Chip). Benny dies before he can activate the Securitron Vault. At the battle of the Dam, the NCR wins out over the Legion, but are completely exhausted from the attacking Legion Forces. General Oliver of the NCR was also captured by the Legion during the retreat. President Kimball was assassinated by a Legion Sniper. Colonel Hsu is moved to the front lines, and irradicates the rest of the Legion Army in the Mojave. The Legion is gone, and the NCR can;t defend itself. Government never comes to the West. So...

What happens now? All the Major Factions have been knocked out, so who ends up ruling the Mojave? You can pick whichever faction for whatever reason (their your favorite, best weapons, best armor).

Personally, if the Followers of the Apocalypse (my favorite) and the Enclave (My second favorite/best tech) teamed up, I think they would dominate the Wasteland with knowledge and Power. The BoS would probably be wiped out before the Battle of Hoover Dam by the NCR, which means that the Enclave/Followers Team-Up would eventually discover their armor and weapons, and would basically make them invincible.

Enclave is gone, people. Get over it.

I'd say it would be total anarchy. Everyone taking what they want.

Arcade Gannon get's thrown out of the Followers of the Apocalypse after a lifetime of work because they found out his parents were Enclave in one of the endings. The Followers of the Apocalypse would never work with us.

Why would the Followers ally with the Enclave? I think the Mojave would revert to how it was before the NCR showed up at the dam and be that way until a new power arose. The FoA don't have the numbers to create a government, and I don't see the desire. Maybe that would change in 20+years. I doubt the NCR would wipe out the BoS before Hoover Dam. They don't have the manpower to take out the BoS before the dam because of the Legion. The BoS do not have the manpower to take over the Mojave; again, maybe in 20+ years. I see the lockdown ending and their overall state improving. Maybe they can get new members from other chapters. Yes Man is the wild card. Without anyone to boss him around, he would probably become assertive much quicker and start running things in Vegas. It wouldn't be as hard to find the chip this time; providing it wasn't destroyed. He could then reactivate the securitrons in the vault. Yes Man has the best chance of taking over the Mojave.

The fiends would take camp mccaren, and basically wipe out the most of the mojave

The fiends? Come on man!
What about the Brotherhood of steel? Not that i like them but it seems to be the most possible way.

The BoS would continue to sit in their bunker, wearing their tinfoil hats.
The Enclave would continue to not exist in any meaningful way.
The Kahns might team up with either the Fiends or the Powder Gangers to raise hell, otherwise they'll be too weak to do much.
On their own, the Fiends and Powder Gangers are too fragmented and disorganised to do anything but sporadic raiding.
Boomers would sit in their airbase being xenophobic.
The Three families would either kill off each other or band up to keep Vegas safe for a while
The Kings would either be killed off by the Three Families or raiders, or team up with FotA to be their muscle.
FotA would run around, shouting for everyone to be friends.

Business as usual, for an uncivilized part of the wastes ^^

Since NCR is gone Khans would move to a more prosperous area but I don't think they'd "take over" Vegas, that city life ain't for them.
Of the three families on The Strip I believe that The Omerta's would win and take control over Vegas.
Tops' members aren't exactly as well equipped and White Glove society, while cannibals, aren't exactly battle hardy.
And then we have Powder Gangers, they would take over the outskirts of Vegas, Primm, Novac, Nipton, Goodsprings and raid caravans and other members.
Boomers would sit on their asses.
FotA would probably stick around, see no reason for them to be kicked out by anyone.
Kings would rule over Freeside but Omerta still rules Vegas, meaning, if they tell Kings to stop doing something, they "will" stop doing that.
BOS, without the NCR or Legion forces would return to Helios One and continue scavenging for pre-war tech since none of the factions in the area have the firepower or quantity of men to go against them.
Jacobstown would be Jacobstown.
Raul would marry Tabitha.
Davidson would find out that the Bright Brotherhood are space traveling smuggler ghouls which hid stealthboys in their cargo in the spaceships and killed them all.
Boone would become a slave at Omerta where he does rather disgusting things for the customers.
ED-E would never be repaired. D=
Cass is now a skeleton, still sitting there in the bar with a whiskey glass in her hands.
Arcade married No-Bark at Camp Searchlight, they both died from being cannibalized by feral ghouls shortly after the wedding ceremony.
Lily found her daughter, Orris, and due to her delusions she wanted her back in her tummy, so she ate him. =D
Rex died a painful and slow death from his brain rotting away.
Veronica found her dress.
And Sunny Smiles was eaten by her dog Cheyenne.

well thats too bad cause the enclave were awesome enemies to fight as well as the supermutants in FO3, they fired long range weapons were very tough, new vegas doesn't have tough enemies except for all the melee enemies, the enclave are a high evil type faction and thats missing from new vegas, there aren't really any high tech factions similar to the enclave and the enclave were fun to fight and tough, so maybe fallout 4 will have an enclave type faction, people say tired of the enclave, well they;'re more fun to fight than scorpions and deathclaws, humans always make the best enemies, animals and creatures are as fun to fight in games as people.