The Masamune and Muramasa's status as Public Domain Artifacts and their frequent appearances in JRPGs like Final Fantasy and Chrono Trigger may lead some gamers to assume that they are mythical swords, like Gram or Excalibur. In fact, they're real-life masterworks more akin to a Stradivarius instrument. Not only were Masamune and Muramasa historically real swordsmiths, there wasn't even "the" Masamune or Muramasa blade; several specimens of both still exist today in museums and private collections, and they occasionally appear at auction for the sufficiently lucky and/or wealthy collector to obtain. (That said, "the" Masamune is often considered the suitably storied (and suitably lost) Honjo Masamune.)
Also, lasers on aircraft for direct offensive purposes sounds completely science-fiction, especially considering the weird airplane it's mounted to that literally opens up to aim the laser in the games... but lasers were actually considered as a method for intercepting ICBMs. They were completely impractical for it for various reasons, which the series itself lampshades when the actual YAL-1 shows up for a mission in Ace Combat Infinity to shoot down a missile... and gets shot down itself before it can do anything.
At one point in Alpha Protocol, nutbar conspiracy theorist Steven Heck asks the protagonist, à propos of nothing, if he knew the CIA once wired a live cat with radio equipment back in the 60s. Operation Acoustic Kitty reallyhappened.
Army of Two's mechanic of inserting a tampon into a bullet wound as emergency care received much derision from professional reviewers despite the developer's insistence that their consultant told them (and as some independent investigations have concluded) this is something some real armed combatants actually do. Hell, that was the whole reason tampons were invented in the first place before the feminine hygiene applications were realized.
The Carmagnolle suit is also shown on the inner cover of Juno Reactor's The Golden Sun of the Great East album.
During her gag reel in BlazBlue: Chrono Phantasma, Makoto has her tail snapped off by Taokaka, which Kokonoe chalks up to Makoto having traits from the Kagutsuchi Island Squirrel. In reality, some species of squirrel actually can have their tails snap off as a one-time defense mechanism against predators.
"Dr. Ryuta Kawashima" isn't a character Nintendo created for the Brain Age series, he's a Real Life Japanese scientist whose research inspired the creation of the games.
Among the many issues fans take in regard to historical accuracy in Call of Duty: WWII is that there are a number of Soviet-made weapons being used by Wehrmacht in both the multiplayer and single player modes. However, the Wehrmacht did field a number of Soviet weapons in their arsenal. Following the first successful months of Operation Barbarossa, the German military acquired so much Soviet material that they issued them to second-line troops. Among the most popular of these were the PPSh-41 Sub-Machinegun and the SVT-40 semi-automatic rifle; the latter was in such widespread use that the Germans issued field manuals for them. In addition, the period in which the campaign takes place is towards the end of the war, when the desperate Germans were issuing whatever they had in storage to front-line troops in the face of the Allied bombing campaign's destruction of their industrial infrastructure.
Crimson Skies (The Diesel PunkTrope Codifier of Video Games) has Zeppelins that carry most of the planes and deploy and dock them mid-air using a trapeze hook. Seems unrealistic but it is a real technique for operating aircraft from zeppelins.◊ Want to shoot one down? Easy right? Not in this game. This is surprisingly realistic, since many of the airships of the time were either helium-filled or using a hydrogen/helium double-cell system, and even pure-hydrogen rigid-frame zeppelins are surprisingly hard to ignite without incendiary/explosive rounds. Rockets, on the other hand...
The "Cadaver Synod" global event that pops up in Crusader Kings II whenever a Pope with the "Wicked Priest" dies, in which his successor digs up his corpse and puts him on trial for his crimes posthumously, is sometimes assumed to be yet another of Paradox's tongue-in-cheek gags by new players — but the inspiration is entirely historical.
The Division 2: The resident PMC faction fields a rather bizzare-looking Robot Dog that doesn't have a visible head and has the knees of each pair of legs pointing inward. This particular robot is based off a real one calledBigDog, initially developed by DARPA before being contracted out to Boston Dynamics.
Some of the more memorable enemies of EarthBound are its animated enemy trees which explode when defeated. Not quite as far-fetched as one would think: Australia (no surprises there) is home to the eucalyptus tree genus, which are prone to exploding when exposed to fire. Admittedly, they don't look much like EarthBound's exploding trees (which the English translation refers to as oaks, anyway), and they certainly aren't animated or otherwise trying to kill you (at least, not intentionally trying to kill you). However, according to Wikipedia's "exploding trees" article, other kinds of trees can explode if the sap expands due to being frozen.
Ebony is a series' staple of a high-tier Fantasy Metal, functioning somewhat like Obsidian and theorized to be the petrified blood of the mortal world's "dead" creator god. Ebony does exist in real life, however, it is not a stone. It is actually a dense black wood taken from ebony trees found in India and parts of Africa. It's so dense it sinks in water, and is mainly used for ornamental stuff like chess pieces and piano keys.
Wherever they appear in the series', Tamriel's native Sabre Cats have large, stocky, bear-like bodies as opposed to the sleeker, more slender appearance of modern real-life big cats. This understandably gives players the impression that Sabre Cats are are fantastic hybrid animals, like a griffon or a manticore. They are actually pretty much one-to-one copies of the genus Smilodon.
Many farms in the game feature shaggy big-horned bovines that are labelled and referred to as cows. Their appearance has led some players to mistake them for yaks or claim that Bethesda got things mixed up. In fact, the cows are a very accurate rendering of highland cattle.
You might think Pegnose Pete from Escape from Monkey Island is just a gag on peg-legged pirates, but prosthetic noses are a real thing, and have been for centuries; 16th century nobleman and astronomer Tycho Brahe wore a false nose after getting his cut off in a duel.
One of F/A-18 Hornet's final missions, "Hole in One", has you destroy a nuclear shell-firing "supergun" built on the side of a mountain. One of these was actually partially constructed as part of Project Babylon.
Ditto for the nuclear cars, too. The idea was actually explored with the Ford Nucleon, but we've yet to make any nuclear reactors small enough.
The Fat Man portable nuclear catapult? It's a real thing. The M-29 Davy Crockett Weapons System, also known as the "Little Feller" project, used a mortar-style launch system rather than a mechanical catapult, but the mininuke projectiles look virtually identical down to the paintjob. The project was even canceled for a reason that most players quickly realize shortly after first using a Fat Man: Nuclear Weapons Taboo aside, it is a Very Bad Idea to be standing anywhere near the potential blast radius of a small nuclear missile with unfortunate accuracy issues and no "abort" option once fired. The device is a bit different thing than its in-game namesake, however, which was far larger.
Remember the Punch Gun, or its latest incarnation, the Ballistic Fist? There existed a real version of those gun-gloves, used mainly by spies as a concealed weapon. Not only that, but it functioned the same way- to fire the gun, you had to push down the plunger on the front by punching your target with it.
The company General Atomics International may sound like just part of the pre-War Fallout world's obsession with nuclear power. General Atomics Technologies Corporation is a real and still extant company. They even have robots (specifically, UAVs) as one of their major product-lines. The game's counterpart is overall closer to General Electric though, with its focus on consumer products.
Raven Rock is a real underground military command center. You could be forgiven for thinking it was a Morrowind reference. In fact, the location in Morrowind was named after the real-life complex in Maryland, not too far geographically from the physical location of Bethesda Game Studios.
The abandoned fairground in Point Lookout has a number of White Star pinball machines, which was the real-life name of an arcade system board used by Sega Pinball and Stern Pinball from 1995 to 2005.
Some of the ways mutation and exposure to nuclear fallout affect things in the games aren't too far off from what would happen in reality. As outlandish as Brahmin seem, two headed cattle happen from time to time, even without nuclear fallout involved. The Yao Guai in 3 (not the giant ones in New Vegas) are basically just black bears that lost most of their hair. The idea of mutated animals like this forming new species isn't outlandish either, nuclear testing in the pacific did the same thing with sharks.
The Goodsprings General Store, Pioneer (Prospector) Saloon, and Jean Sky Diving school are all real businesses, although the last is in ruins in the game.
Most of the towns and settlements in the game are real. New Vegas is obvious, and Primm and Boulder City slightly less so, but Goodsprings, Nipton, Sloan, and Nelson are all real towns near the California-Nevada border (though all are very sparsely populated today, with Nipton being the most populous with around 60 inhabitants).
Incidentally, many people seem to think Boulder City is supposed to be (or is based on) Boulder, Colorado, but there is a Boulder City in Nevada, and is the second most populated location depicted in the game after Las Vegas itself.
The Legion's Lottery of Doom in Nipton, believe it or not, is also based on reality. Not the "of doom" part — Nipton was where Nevada residents went to buy tickets for the California state lottery, as Nevada's constitution forbids a state lottery. Incidentally, Nipton lost this appeal when a store just on the California side of the border near Primm was opened. And yes, Nipton's in California despite being southeast of Goodsprings and Primm.
NCR Correctional Facility's real life counterpart is the now-defunct Southern Nevada Correctional Center.
The real world Whiskey Pete's Casino in Primm houses the exhibit of Bonnie & Clyde's death car, who were the basis for the Fallout verse's Vikki & Vance and the casino of that name.
As the above sentence implies, Primm is a real town — its other notable in-game feature, the Bison Steve Hotel (with its rollercoaster the Diablo) is based on the real Primm's Buffalo Bill's Hotel (with its rollercoaster the Desperado).
The Helios One power plant is present in the real world as Nevada Solar One.
Although the town itself is completely fictional, Dinky the T-Rex in Novac is modeled after the Mr. Rex sculpture in Cabazon, California, and named after the neighboring Dinny Apatosaurus sculpture.
One quest has you raise a sunken B-29 that crashed into Lake Mead in 1948, which was a real event, and the real plane is still down there.
REPCONN is an expy of the real rocket fuel production company PEPCON, whose Henderson, NV plant was destroyed by a fire and explosion in 1988.
There is also an actual Old Mormon Fort in Vegas.
Sarsaparilla really does have a history of health scares and sensationalist reporting- the sarsaparilla plant was mixed with Sassafras in many traditional root beer recipes...until it was discovered that a major component of sassafras oil, Safrole, is both carcinogenic and has multiple adverse metabolic effects. While sarsaparilla itself is fine, the link has lead to periodically resurfacing urban legends misblaming sarsaparilla as the toxic component thanks to confusion between "sarsaparilla the alternate name for root beer" and "sarsaparilla the plant".
You can't, however, see the Statosphere (the inspiration for the Lucky 38) from Primm in real life. And the Stratosphere doesn't dominate the Vegas skyline in general the way it does in the game. Granted, this is because other major landmarks like the MGM Grand or Caesar's haven't been blown up in reality.
There are several real-life vintage hamburger stands named Dot's Diner. The one in Bisbee, AZ most resembles the chain in the Fallout verse.
Far Harbor from the Fallout 4 expansion of the same name is based on a real town, Bar Harbor, on Maine's Mt. Desert Island, and Acadia, the synth settlement, is the real-life name of the national park there.
The Jamaica Plain settlement is located in and named after a real neighborhood of the southeast Boston area.
Although the Sanctuary Hills neighborhood doesn't exist in real life, the Old North Bridge leading to it does, as part of Minuteman National Historical Park.
Speaking of Sanctuary Hills, one might think that the houses in this neighborhood are merely a result of the developer's imagination. However, they're actually a very accurate reproduction of Lustron Homes - a style of house that was assembled, rather than built, from 1948-1950. The largest remaining collection of such homes exist on the U.S. Marine base in Quantico, Virginia, and thanks to their porcelain coated steel plating, look very much like they did when they were first built.
The quest "Trouble Brewin'" has you recover a beer-brewing robot named Drinking Buddy. Two years before the game's release, a team of North Irish beer craftsmen, with the aid of Kickstarter, developed a real automatic brewing machine, appropriately named Brewbot.
The Boston Mayoral Shelter is a thing in real life, except it's called the Massachusetts State Emergency Operations Center.
Speaking of the lottery in Nipton, a radio broadcast mentions that the brutal Legate Lanius has instituted a form of punishment where he divided a group of Legionares into groups of ten, and had the tenth man beaten to death by the other nine. This may sound like a typical example of post-apocalyptic brutality, but this was a real practice in the Roman army, from which modern English speakers get the word "decimation", with the unfortunate tenth man determined by drawing lots.
Kiara Sesshouin from Fate/EXTRA CCC and Fate/Grand Order is a Buddhist nun whose entire schtick is that she was taught to embrace carnal desire and wishes to push her Buddhist sect's philosophy upon the entire world. Sounds ridiculous since a major part of Buddhism is about abstaining desire, right? The Buddhist school of thought that preaches sex as one way of becoming closer to Buddha, the Tachikawa school, is real and was formed in the twelfth century as an offshoot of Shingon Buddhism.
Final Fantasy VIII features the main character, Squall, wielding what's called a "Gunblade", a Combination Weapon of a pistol and a sword. Most assumed there was no way on earth something like that could have existed. It did, actually. Of course, it wasn't exactly a practical weapon.
That being said, Squall's weapon is explicitly a triggered Vibro Blade...which also exists, but with the much more mundane utility of electric carving knives.
The same cam also be said about Monster Hunter's Gunlance, which is essentially a giant version of a Pistol Sword.
In Fire Emblem Awakening, some people thought that Lissa's dress◊ was unrealistic and too over the top. Actually, it was inspired by wire-cage dresses which actually do exist.
The premise of Five Nights at Freddy's 3 is that, 30 years after the first game, Freddy Fazbear's Pizzeria has been reopened as a horror attraction in response to in-universe Urban Legends. While a few people found it strange, many locations with gruesome or unpleasant histories do tend to gather tourists in the real world (examples include the house where Lizzie Borden killed her parents, locations where Jack the Ripper is said to have killed people, submarine trips to the Titanic, and countless others). Some people just have weird tastes.
Most, if not all, of the locations in ForzaHorizon 3 can actually be found in Australia. This includes cities such as Surfers Paradise and Byron Bay as well as landmarks such as Maroondah Dam and the Twelve Apostles.
The Grand Theft Auto series has a Running Gag of making Fun with Acronymsexpies of real life police forces, such as N.O.O.S.E, so you'd be forgiven for thinking that C.R.A.S.H. is another silly Rockstar joke. Not only was it a very real former spec ops division of the LAPD, but San Andreas' Big Bad, Officer Tenpenny and the leader of C.R.A.S.H. in the game, is an Expy of Rafael Antonio Pérez, one of the real-life C.R.A.S.H.'s most notorious members. Amusingly, if anything, the GTA version of C.R.A.S.H. is less corrupt and over-the-top than the real organization was; the real group had more than 70 proven corrupt officers, whereas the SA C.R.A.S.H. is limited to two corrupt officers and one less-than-willing accomplice.
The antlions from Half-Life 2 are indeed named after a real insect (though real-life antlions share almost nothing in common with Half-Life's, except that they both like to hide under sand), in contrast to the obviously-fictional bullsquids from the first game.
The antlions depicted in Sim Ant, however, were shown perfectly accurately.
Another appearance by antlions is in Pokémon— the Trapinch line are based on them.
Many a Pokemon fan complained about Trapinch's seemingly random evolution from a small, orange, big-headed bug into a green dragonfly-like creature, not realizing that it's based on the actual life cycle of the antlion.
The majority of fans don't realise that "Master Chief" (or, more formally, Master Chief Petty Officer) is an actual rank in the US Navy. This has been exacerbated from the rank's use in fiction being heavily subject to the One Mario Limit, and other Master Chiefs in fiction tend ot have their rank glossed over and/or only referred to by the "MCPO" abbreviation.
Many of the UNSC weapons in the series are based on real life weapons, such as the shotgun with its strange, top-loading feature being based on the South African Neostead 2000. The development team actually had to cut some of the odder features of the real guns, like the Neostead working by pumping forward instead of backwards and having two magazine tubes (something which only became relatively commonplace in real life after Halo 3 or so), or the SMG's original reloading animation, which would had included pushing a 'stick' of caseless ammunition into the feed port, then breaking it off to avert One Bullet Clips. For extra fun, the Assault Rifle of the first game was designed as a concept of what a futuristic bullpup assault rifle would look like, but between nailing down the design and releasing the game, the F2000 was released, and ended up heavily featured in another popular Xbox game just a year later.
Kingdom Hearts has Sea Salt Ice Cream, which is a favorite of many a character from the second game on. It sounds too weird to exist and if it did, the salt would lower the freezing point of the mixture, making it difficult to maintain a solid form in the real world. Not only does this stuff exist, it's sold in Tokyo Disneyland, where the creator of Kingdom Hearts tried it and loved it so much he put in the second game.
In Kingdom of Loathing, one can mine for asbestos ore (a fibrous material used in fireproofing, until it was discovered that tiny particles of it tended to get everywhere and foul up people's lungs). There's a whole family of different minerals called "asbestos", you do mine for them, and some of them are chunky. Although the Kingdom of Loathing version was created when prehistoric fire-breathing dragons died and then were buried in landslides and such, undergoing a process similar to the creation of crude petroleum, which is probably not how the real thing forms.
The ocarina, featured in The Legend of Zelda: Ocarina of Time, was a real musical instrument, present in many world cultures, sometimes for millennia. The model as seen in the game was developed mid-19th century. Not only is the ocarina a real instrument, there was a real version of the ocarina from the game made and sold. It looks exactly like the one in the game and is playable. Unfortunately, you can't toggle night/day with it, nor can you use it to teleport yourself.
The rupee is a real currency, used in places like India and Pakistan. Although, real rupees are represented by coins and bills like most other modern forms of currency, not colorful gems.
At first glance, the large-beaked Loftwings from The Legend of Zelda: Skyward Sword might appear to look that way because of the stylized cartoonish aesthetic of the game. They actually look almost exactly like the real life Shoebill.
This may have been the case in terms of the weaponry, since they sounded and looked exotic enough to a lot of gamers first exposed to them. Every weapon is real, except the Nikita (though the concept is in missiles such as the TOW - the only outright impossibility is how slow the missile moves without dropping into the ground) and personal chaff grenades (chaff is usually an aircraft thing). Since then, these weapons introduced in the series have become staples of video game arsenals, in some cases moreso than in reality (the SOCOM pistol and FAMAS rifle having since dropped by the wayside due to issues with weight, performance, and/or budget).
The Ear Pull event that Vulcan Raven mentions is a very much real event designed to test endurance, although some Arctic Sports communities have banned it due to the squeamishness of their audience and the inherent danger it poses to the competitors (bleeding, stitches and the like). The Stick Pull and Four Man Carry events mentioned in The Twin Snakes are also real events in the Eskimo-Indian Olympics. Even the Muktuk Eating Contest mentioned in the PSX version is a real event, meaning Snake wasn't just being snarky about Raven's size.
There's a part where Sigint tells Snake the story of a unit of Russian "bomb dogs" during World War II, who were to be used to destroy tanks (and failed because the Russian tanks had been used for the training, causing the dogs to attack them instead of the German Panzers). Since he describes it as a secret military project, it's safe to assume it's just the usual Hideo Kojima insanity and just another detail in a game about psychic bee soldiers and electric megalomaniac Communists. It isn't. The bomb dogs were real and the plan ended up that way.
Additionally, the flying platforms seen in Metal Gear Solid 3 were jet versions of this experimental U.S. aircraft. Oh, and the drone used by Naked Snake at the beginning of Operation Snake Eater, and the WIG? Bothreal.
The flying platforms were actually a real thing. They really flew. Their main drawbacks were their short flying time, difficulty to fly, and incredible vulnerability and lack of redundancy.
And the Shagohod. One look at the Shagohod and you might think Kojima was going overboard with the mechanical designs. Thing is, however, there really were tanks designed to fire nuclear artillery. They don't actually function like the Shagohod does.
Speaking of tanks and the Shagohod. Those tanks that Snake briefly saw at Groznyj Grad, which Volgin later destroys while rampaging across Groznyj Grad? those were actually real, and Sigint's description when calling them is also their real history (although there were more factors to their cancellation besides simply a lack of funds).
A lot of people think CalorieMates are a fictional product but you can actually buy them in Japan. In fact, the only fictional products in the entire series are probably the cigarettes.
For those who are skeptical enough to believe that the Markhor is a fictional animal (considering Metal Gear Solid 3 has added fictional animals like the Baltic Hornets), they will be surprised to know that the markhor does exist and that its name really does mean "snake eater."
Speaking of Baltic Hornets, while they certainly don't exist, the Japanese Giant Hornet certainly does. Their name in Japanese is ōsuzumebachi which translates to "giant sparrow bee". Not only are they Bees in Japan, they are a major threat to honey bee hives. The hornets will sniff out honey bees, and pillage their nests, literally butchering entire colonies of bees before hauling all the honey and delicious bee-torso steaks they can stuff into their home nest. It seems the bee/hornet confusion may be more a result of Lost in Translation than Artistic License Biology.
The code phrase Zero gives Snake is "Who are the Patriots?" to be responded to with "La-li-lu-le-lo". This sounds like a nonsensical reference to the previous game, but (as Kojima notes in the director's commentary) it is based on two real shibboleths used historically by Japan in wars - "ga-gi-gu-ge-go" and "ba-bi-bu-be-bo".
It must be noted, though, that it does not work the way it is depicted in the games (with the balloon rapidly whipping the load into the sky through its own buoyancy). The balloon only carries one end of a long cable to a high enough altitude that an aircraft equipped with special arms on its nose can engage it safely. Afterwards the load is winched in.
The parasites in Metal Gear Solid V have many impossible qualities, but some of their traits are based on real life parasites: infected characters have notable alterations to their lungs, muscles, nervous system, skin, and eyes all areas where Toxoplasmosis symptoms occur. And there is a real-life parasitic fungus that grows into the brain of infected ants and causes them to climb to high places in order to spread spores further. Additionally, Wolbachia really changes its host's sex from male to female.
Japanese city-building game Metropolismania featured several real-world store chains, such as U.N.I.Q.L.O., which were little-known outside Japan.
Even the most die-hard Mortal Kombat fans may be surprised to hear that the Lin Kuei was (and is) a real organisation. However, they had very little to do with the ones in the games (they were not actually ninjas—they were more like a secret monastic order of Crazy Survivalists), although there is a mostly-discredited theory that they inspired the Japanese ninja, as in the games.
Namco Museum Volume 4 for the original PlayStation contained an arcade game called Genpei Toumaden, which up until then had not been released in North America. Retitled The Genji and the Heike Clans, the game features a "character" called "Taira no Kagekiyo". A number of American game players may or may not know that he isn't a character created by Namco for the game. Kagekiyo was a true historical person. A member of the "Taira" ("Heike") clan, he fought during Japan's "Genpei" Wars where he died in battle. In the game, he comes back to life and seeks revenge on the Genji clan.
Most of the Nancy Drew games are about solving riddles a dead person left to help find a treasure they hid. Believe it or not, people have hidden treasures and written cryptic riddles as to how to find it. 
Certain Need for Speed games show the local PD employing some six-digit exotics to chase down lawbreakers that most taxpayers would probably vote against in real life. However some law enforcement agencies (particularly in Europe) really do have some very nice wheels, such as a Lamborghini Gallardo that currently serves in an Italian police force interception squad. Some British police forces have adopted the Subaru Impreza WRX or Mitsubishi Lancer Evolution, popular cars in the Real Life tuner scene, for motorway policing duties on the grounds that it takes one to catch one.
Normally one won't encounter such vehicles unless their "Wanted" level is really high. And true to life, police officers won't bring out the souped up cars unless their normal Crown Victorias can't keep up with the perp. Also such vehicles are normally employed by the higher level law enforcement, like state highway patrol officers or county sheriffs.
William Adams, the player character of Nioh, is based on a sailor for the Dutch East Indies Company who actually became a samurainote Doing so alongside his second mate, Jan Joosten van Lodensteyn, though as only as an advisor to Tokugawa Ieyasu rather than as a demon slayer. He was also English, not Irish. Further, he was actually the sixth foreigner to become a samurai, the first being an Africannote Possibly from Mozambique man named Yasuke, who was a retainer to Oda Nobunaga. You meet him late in the game as a boss.
Payday 2: ECM Jammers are, in fact, a real thing. For pretty obvious reasons, they're banned almost worldwide as they intercept nearby phone and radio signals and mix up the frequency into an incoherent mess nobody on either end of a call can decipher.
Before Wikipedia or the Internet, it was difficult to explain that Pokémon were inspired by mythological animals (for example, Magikarp's evolution into Gyarados is based on the legend of the "Dragon's Gate", a waterfall that will turn any carp that swims all the way up into a dragon).
Moonstone and sunstone are actual semiprecious stones. They might not have the same powers, or form a set of elemental stones.
A lot of Pokémon are also based on real-life animals that are better known in Japan than in other parts of the world. Manaphy and Phione are based on sea angels, for example.
Although the regions might seem like a fictional world, several mentioned places like Tunguska in Russia are recognised as real places.
All of the regions in the games are based off real places, mostly in Japan. For instance, the Kanto region is named after a part of Japan, and several of the towns correspond to real cities in the area (for instance, Vermillion City is based on Yokohama, and Saffron City and Celadon City are supposed to represent different parts of Tokyo). Even the Cycling Road is based off a real bridge, which was being built in Tokyo Bay during the game's production.
With all the weirdness and silly humor associated with Portal, you'd think that Cave Johnson's moon rock poisoning was just another silly joke. In fact, lunar dust is an actual hazard to humans. It's just as destructive to human lungs as asbestos, since it's just as sharp and brittle unlike earth dust, which has been rounded by natural actions (wind, rain, etc) that don't exist on the moon, and you will die a slow, horrible death if you breathe in too much of the stuff.
Rainbow Six Siege's limited time event Outbreak takes place in Truth and Consequences, New Mexico, an actual city.
Almost all of the secret projects in the Sniper Elite series are real Nazi projects. Some are just more believable than others. While most people know some things like the V2 Rockets in Sniper Elite V2 is famous enough that people know it is based on the real thing, others may look like Stupid Jetpack Hitler projects. The Ratte in Sniper Elite 3 is a real proposed land battleship project which was eventually abandoned due to being Awesome, but Impractical. The radio guided Fritz-X bomb in Sniper Elite 4 is a real thing, and is the same bomb responsible for sinking the battleship Roma and severely damaging many other ships, including the Warspite.
Meanwhile, his daughter Ivy uses a sword that breaks off into several sections and takes on the properties of a whip. Although they don't function quite like that in real life, swords with whip-like blades do exist.
Splatoon 2 has a couple of off-handed mentions of a place called "Mount Nantai" in various character dialogue from the single-player campaigns. Made up for the game? Nope—as you might be able to tell from the lack of fish puns in its name, it's a real volcano in Nikko National Park on Honshu, not far from Tokyo (which Inkopolis is implied to be a far-future version of). It's well-known inside of Japan, but foreign audiences probably only know it from this game.
In Wolfenstein II: The New Colossus, one of the player's allies is a Communist Christian named Horton Boone. Whilst Communism is predominantly thought of as an anti-religious philosophy, and some of its founders did issue strong statements against organized religion, Christian Socialism was - and still is! - a real thing, arguing that Socialism is the kind of government structure that Jesus would support and wish for humanity to adopt.
Baslam in Ys: The Ark of Napishtim is a merchant who built a town, gathering the stone by dismantling ruins of priceless historical value. It sounds like a comically over-the-top bit of Corrupt Corporate Executive behavior, medieval fantasy-style... unless you know this has actually been done in real life. Multiple times. Medieval Cairo was built by raiding limestone from the pyramids, the Renaissance Italians would tear marble off of Roman buildings and melt down statues in order to get the materials needed for their own works, and numerous houses built in the immediate aftermath of the English Civil War contain identifiable pieces salvaged from castles destroyed by artillery.