There's a very subtle one that they really had to do the research to dig up - there's a minor, otherwise unimportant member of the gang known as The Kings carrying a unique barber's razor called Figaro. Examining the map reveals that the location he is found in corresponds almost exactly to the location of the real life Figaro's Barber Shop in Las Vegas.
The unique variant of the Tesla Cannon known as the "Tesla-Beaton Prototype".
La Fantoma is obviously the female, Hispanic version of The Phantom.
Alternately, she's an Expy for an Expy, with the Bowdlerized Latino version of Fantomas, who's portrayed as a sneaky superhero rather than the original source material's Complete Monster.
The cover is also a mirror image imitation of the Adventure Comics origin issue of Black Orchid.
One of the sidequests involves a former Omerta trying to free his "dancer" girlfriend from her life at Gomorrah and running as far away from New Vegas with her as possible. His name? Carlito.
Vault 11's premise is heavily based upon The Lottery, although with an additional Take That to political parties that use an ostensible democracy to undermine the good of its own citizens.
The name of one of the casinos, Gomorrah, could possibly be a shout out to a joke from Sister Act.
(On seeing Reno for the first time) Sister Mary Robert: It's beautiful!
Sister Mary Patrick: And what a lovely name, Reno!
You can find a BFS made of a car bumper that's about seven feet long. What's it called? The Bumper Sword.
A dead prospector located in a heavily irradiated area called the Devil's Throat bears a strong resemblance to Duke Nukem.
Those versed in US finance will recognize NCR bear and the Legion's bull as symbols of the stock market, the bear and the bull traditionally representing a falling and rising market respectively. The NCR falling while pushing east, and the Legion rising with their conquests.
Kudos if you noticed this one: On every single street lamp in the game, there is a tiny plate with TES4.
A unique weapon in the game is "This Machine", named after Woody Guthrie's guitar "This Machine Kills Fascists". In response to that name, the phrase "Well This Machine Kills Commies" is written on the side of the gun.
A really subtle one is a skeleton in the wasteland can be found lying on the ground with its arms reaching towards a first aid container. It looks eerily similar to a lot of dead NPCs in old FPS games like Half-Life, where trained soldiers had an odd habit of dying right next to med kits.
During the quest "How Little We Know" you meet a man who's indebted to the Omertas because they helped him cover up his accidentally killing a prostitute during a drug-induced blackout. Now why does that sound so familiar?
Wild Wasteland
Let's just say that Goons will be playing in utter glee with an appearance from Johnny Five Aces and company, not to mention the YCS/186 Gauss Rifle. Your Console Sucks is a subforum on SA, and its ID number is 186.
Just outside Goodsprings you can find a refrigerator with a skeleton in it. It's wearing a brown fedora. May double as a Take That, since many people couldn't get over the fourth film's nuclear explosion.
On the wall in Cottonwood Cove (a Caesar's Legion outpost) is graffiti reading "Romanes eunt domus".
In Nipton you find a pair of clothed, charred corpses outside of a house named Owen and Beru.
One of the more subtle Wild Wasteland occurrences is when you're exploring a disappearance in the casino of the White Glove Society: you discover the body of a fellow detective, a sunglasses-wearing man by the name of Caruso.
Also, at the basement of the church in Searchlight, one can acquire fivethree Holy Frag Grenades.
It was cut from the final game, but the game files show that there was supposed to be a creature that could only be encountered in Wild Wasteland: A unique Fire Gecko that had it's own unique breath weapon, was 3 times larger than normal fire geckos, and could best the Legendary Deathclaw in combat, making it the most powerful creature in the game. When spawned with the console it's just "Gecko", but it's name in the editor is Gojira.
The plot involves robbing a great treasure from the Sierra Madre. Bonus points for it causing previously amicable seekers to grow greedy and kill each other over it.
Honest Hearts
With Wild Wasteland, one of the tribals is named "Two-Bears-High-Fiving". This is in reference to a rather peculiar New Vegas mod. The mod's author was apparently very bothered by the fact that there's no dialogue that states one of the Rorschach ink blots Doc Mitchell examines you with looks like two bears high-fiving. Said mod is solely dedicated to adding that single dialogue line in.
Also with Wild Wasteland, talking to White Bird the shaman about the Rite of Passage causes him to say "Take drugs, kill a bear", a reference to the Advice DogImage Macro.
Old World Blues
With Wild Wasteland, Dr Mobius will mention that he has several 'Plan 9s in place.'
The Book Chute telling you how to do your own "re-indoctrination" which needs "a cage that fits over your head and a bag full of mole rats". You also find his backup Personality Module in House #101. Plus, he's one big shout out to Fahrenheit 451.
Quite a bit of Old World Blues makes subtle reference to The Venture Bros., with Dr. 0 being voiced by James Urbaniak (the voice of Rusty Venture) and having his personality and many of his lines lifted directly from the show.
Dr. Klein, although not voiced by the same actor, sounds suspiciously like Jonas Venture from the same show.
Dr Borous said he created Nightstalkers and Cazadores back before the war, he can't remember exactly when, but he rememberedit was Tuesday.
In the doghosue behind Dr. Borous's house, you can find a minituare Deadthclaw named Spike
In one of the research labs, you can observe a room with Cyberdogs sitting around a table... playing poker.
Lonesome Road
Nuking both NCR and the Legion at the end of Lonesome Road with Wild Wasteland on will turn a part of Ulysses' closing narration into an almost word-for-word reference to the infamous ending of Planet of the Apes.
With the Wild Wasteland perk, the Fist of Rawr Deathclaw Gauntlet becomes the Fist of the North Rawr.
Fan FilmFallout Nuka Break gets one in this DLC, before it's even released! A new unique rebar club is added in the game. It's name? The Nuka Breaker.
Now that it's out, it's special move is in fact called the "Nuka Break."
One of the One-Star Challenges added is A Slave Obeys. For those who never played Bioshock, you kill Mr. House with a golf club.
Another assassination-related Challenge is "Even A God-King Can Bleed", which you get for nailing Caesar in the head with a throwing spear.
Two of the other One-Star Challenges added - namely, "The Same Could Be Said of All Religious Weapons" and "You Don't Belong In This World!" - are taken from the (in)famous intro of Castlevania: Symphony of the Night.
The special move for the Katana is called Unlabored Flawlessness. Unlabored Flawlessness is one of the most powerful weapons from the first game of the Xbox Ninja Gaiden series.
One of the challenges is "A Benefit or A Hazard," for destroying robots with That Gun, which was designed to resemble Deckard's gun from Blade Runner.
There's a challenge for killing either NCR or Legion assassination teams with a revolver called "Dyin' Ain't Much of a Living".
The challenge for killing Caesar with a knife is called "Historical Propriety", as it's a repeat of how the original Caesar went down. Bring Arcade Gannon for added bonus, as he has the historical knowledge to appreciate your effort.
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