Artax:That Which Man Was Not Meant To Know was taken! Yeagar: By who? Artax: By a foe Lakressa knows only as She Who Must Be Obeyed! Nodwick: Dare I ask where 'she who' went? Artax: To a place called The Lands That Know No Name! Nodwick: Uh-huh. Let me know if we stumble upon any proper nouns in all this mess.
Several characters in Daily Lives of High School Boys were only given a description, such as "Takahiro's friend," "Yoshitake's older sister," "Yanagin's Sempai," and "overly self-conscious girl." Downplayed by "literature girl;" later in the series her classmates called her by her nickname "Yassan" despite continued to be known as the "literature girl" on the cast sheet.
Excel♥Saga has "That Man." He has five colleagues, named "That Man Over Here", "That Man Over There", "This Man", "This Man Over Here" and "This Man Over There". It's a subversion, though, as those are their actual names.
Most of the bijuu in Naruto. Because humans don't consider them anything more than huge, destructive monsters, they don't bother learning their names. The only bijuu who is called by his actual name by humans is Shukaku. All the rest are called by the number of tails they have, though Naruto is happy calling the yonbi "Son" and probably will start calling the kyuubi "Kurama."
Shakugan no Shana has Guze no Tomogara, who are often referred by elaborate titles rather than names. Or maybe those titles are their real names. Flame Haze also get such titles, the titular heroine didn't have a normal name until the beginning of the story.
Slayers has "The Lord of Nightmares", also known as "Mother of all Monsters". No name is ever given to this being, despite all it's children having both names and titles "Gaav, the Demon Dragon King" for example.
In The Sandman, there's the Soft Place, a mysterious place that's disjointed from time.
In the Garfield's Nine Lives short "In the Garden", The Crystal Box, or, at length, The Crystal Box On A Checkered Toadstool.
Shade, the Changing Man himself doesn't know what the Area of Madness is. When he asks about it, the most conclusive answer is "The Area of Madness is just one part of The Area."
Kyon Big Damn Hero plays this trope with "Haruhi's favorite website", as the fic usually refers to it with a that phrase or a variation of that. But, as the fic tells it's that website is a wiki and it inspired the Trope-tan anime, it also doesn't try to hide which website it is.
The titular... whatever it is... in an H.P. Lovecraft parody called "The Indescribable".
The monsters who hold The Village in fear are called "those we do not speak of".
In Armageddon, character several times refer to "The Russian space station" instead of just calling it by its proper name "MIR" — though it's technically MIR with bits stuck on to make it more impressive. Trevor Rabin's score for the movie includes a cues titled "Death of MIR."
12 Angry Men, the play, never names the jurors, even in the script (they are referred to by juror number). The TV adaptation names a few of them in a tacked-on postscript, though there's no significance to the names.
Kevin Costner's character in Waterworld is known as "The Mariner".
In Kill Bill volume #1, they go through great lengths to hide the name of the Bride (even to the point of bleeping it out). Then in volume #2 it's blurted out to be "Beatrix Kiddo".
But when she buys a ticket at one point in Volume One, her name is clearly visible on her ID.
In Paint Your Wagon, one of the two partners in a gold prospect is simply known as "Pardner" for the entire narrative, even by his wife, but at the end:
Ben Rumson(the other partner): What the hell is your name, anyway?
Pardner: It's Sylvester Newel. Yeah, just one 'l.'
The Dresden Files has the Outsiders; beings hailing from beyond the known cosmos, even beyond the supernatural realms of Faerie, Heaven, and Hell. Three of the most prominent Outsiders in the series have names such as "He Who Walks Behind", "He Who Walks Beside", and "He Who Walks Before". Any other name given to them (such as the pejorative "Sharkface" used by the hero to refer to He Who Walks Before) are explicitly not their true names.
Harry Potter's "He Who Must Not Be Named" (AKA "You-Know-Who"), who is not a No Name Given. Indeed, it's a plot point that Harry himself refuses to use the common euphemisms, and simply refers to him as Voldemort.
The Death Eaters never use his name directly either, referring to him as "The Dark Lord". Snape uses that name as well, which Harry notices.
This is subverted in the final book, where Voldemort turns the superstition to his advantage: since the people who are brave enough to speak his name are precisely the ones he is after, Voldemort casts a spell which allows him to locate anyone who speaks his proper name, even through strong protections meant to prevent just that.
The men of Gondor in The Lord of the Rings (the books) refer to Sauron as "He whom we do not Name" or "the Nameless (Evil)" for short. Elves (and other characters, including Gandalf and Aragorn, both of whom may have picked it up from the Elves) tend to refer to him as "the Enemy".
"The King in Yellow", from the same-titled horror fiction collection of Robert W. Chambers. The King has been borrowed by a number of other authors:
The Lords of Dûs by Lawrence Watt-Evans: the King is the high priest of the also-nameless god of Death.
H.P. Lovecraft used this trope so much that he Lampshaded it in The Unnameable, which not only embodies the trope but discusses it at length.
The humans in The Night Land named most everything outside the Redoubts this way — the Road Where The Silent Ones Walk, the Place of the Ab-humans, the Thing That Nods, the four Watching Things...
In Earthsea Trilogy, knowing the True Names of things is important for spellcasting, so things without names are super-bad juju magumbo.
In the Young Wizards series, the antagonist is usually known as The Lone Power, sometimes as Starsnuffer, or formally as "Fairest and Fallen" (It has many other titles). The "deities" are The One and The Powers That Be.
In Year Of The Griffin, there is a teacher who cannot remember his students' names and so calls them "you with the hat", "you with the hair", "you with the voice", etc. Arguably it's not that he can't remember their names, just that he's such a jerk he never bothers to use them.
"The Place Which Is No More" from David Eddings' Malloreon. note Its name is "Korim", and much of the series is a quest to find just where it is.
Piers Anthony's Battle Circle trilogy features a society of people who are named after their weapon of choice. On a bet, one of the main characters winds up losing his right to use a weapon, forcing him to go forever onwards as The Nameless One.
Non-fiction example: this was a Running Gag in Raymond Smullyan's What Is The Name Of This Book?
Inverted in John Moore's Heroics for Beginners; the Big Bad, Lord Voltmeter, is referred to as "He Who Must Be Named," as Lord Voltmeter dislikes being referred to by personal pronouns.
Presumably the Headless Horseman from The Legend of Sleepy Hollow had a name, but no one calls him by it. Indeed, as he can't speak and has no face to recognize, it's doubtful anyone could call this ghostly figure by his name, even if they'd known him in life and he wasn't a hoax.
Queen Ayesha in H. Rider Haggard's She is known to her subjects as She-Who-Must-Be-Obeyed.
In the Thieves' World universe, the Ilsigi war god is referred to only as Him-whom-we-do-not-name, ostensibly because the Ilsig are a peaceful people.
There is a book named The Name of This Book is a Secret.
In Portlandtown, the chief villain is an outlaw known only as The Hanged Man.
The Stand: Randall Flagg is known as The Man Without A Face and The Walkin' Dude,among other things.
Live Action TV
In The Prisoner, no one in The Village is referred to by name, only by the numbers they are assigned when they get there. Not to mention... well, the very fact that it's referred to as The Village.
Not to mention that when Number Six finally gets a map of the place, the surrounding terrain is marked as "The Sea," "The Beach" and "The Mountains."
And with the exception of Number Six, it's not clear that anyone else in The Village is assigned the same number consistently. Number Two is the most obvious example.
Anyone on Heroes who doesn't know Mr. Bennet's name calls him The Man in the Horn-Rimmed Glasses, despite the fact that his glasses aren't actually horn-rimmed. And his first name, Noah, was never spoken by any character, even his own family, until the end of the first-season finale.
The Haitian, as well. Though he too was eventually given a name, Rene, in the fourth season.
In Star Trek: Enterprise, the blurry 28th-century humanoid who gave the Suliban Cabal their marching orders was never identified. In the scripts, he was simply "Humanoid Figure." Fandom knows him as "Future Guy."
High Priest: The true name is known only by the Keeper of the Name.
Angel: Right. (grabs the priest's neck again) That's you!
High Priest: No, I am the Guardian of the Word!
Angel: You said the word is the name.
High Priest: Yes, and I guard the Keeper of it.
Angel: So you're the Keeper's keeper?
Babylon 5: Shadow minions think it is super-cool that the Shadows' name is a thousand pages long and cannot be pronounced by puny mortals. Then they get shirty because puny mortals continue to call the Shadows "the Shadows".
Personof Interest has the two lead characters often referred to as "The Guy in the Nice Suit" and "The Other Guy"
In Supernatural, Eve, for a time, was referred to as the "Mother of All Monsters", or "All-mother."
In Exalted, all Abyssal Exalted have sold away their names to Eldritch Abominations and taken up weird and evocative titles in exchange. So have the Deathlords they serve. Some examples of such titles include The Lover Clad in Rainment of Tears, Eye And Seven Despairs, the Dowager of the Irreverent Vulgate in Unrent Veils, and the First and Forsaken Lion.
This is parodied in the Exalted stick figure webcomic Keychain of Creation with "Secret", an Abyssal whose adopted name is so long she doesn't even have the proper Stamina score to say it in one breath.
It's also parodied in fandom by tagging the famous ones with much less pretentious versions of their adopted names. The First and Forsaken Lion, for instance, is more often referred by the pseudo-acronym "Falafel."
The Alchemical Exalted also use titles instead of names; in their case, they instinctively know what their title is when they're created. Alchemical titles include such things as Stern Whip of Industry, Lissome Avid Engineer, and Excessively Righteous Blossom.
The Solar with No Name.
Abyssals maintain their poetic names because they are prohibited from recognizing their old names - it is an act of clinging to their old life and the living in general, and their Neverborn masters find that unacceptable, and punish them with Resonance. This is also parodied in Keychain of Creation with Resonance Ben, who is quite proud to admit that Ben is his name, and that when people speak of Ben, they speak of him, because Ben is his name. He actually has certain methods of using Resonance to his benefit (for instance, attacks) so he welcomes the extra ammo. By the way, try doing that in the real game and the Storyteller would be justified in having you shot.
There's one circumstance in which an Abyssal can hear their real name without suffering Resonance: from their Lunar mate.
Speaking of the Neverborn, they are also examples of this trope and for the same reason; all of them invariably having Names to Run Away From Really Fast, such as He Who Holds in Thrall formerly known as Mardukth.
It is more that the Yozis are "Malfeas, the Demon City", "Adorjan, the Silent Wind", "Kimbery, the Sea who Marched against the Flame", while the other Yozi is known only by her title, "She who Lives in her Name", as speaking her actual name causes you to be a possessed drone.
Magic: The Gathering had an entire block, "Champions of Kamigawa" based around Japanese mythology and the Theme Park Version of Shinto. The plot revolved around a human nobleman gaining immortality by stealing something from the godlike Kami, essentially igniting a war between humanity and the spirit world. In the second set, "Betrayers of Kamigawa," exactly what was taken was revealed as the Legendary Artifact..."That Which Was Taken."
The first set in that block gave us the legendary creature "He Who Hungers."
Rise of the Eldrazi contains a card called "It That Betrays", with the cheerful Flavor Text, "Your pleas for death shall go unheard."
The RPG Witch Hunter has an antagonist simply called "The Adversary." He's implied to be the evil spirits (including the Devil) of pretty much every culture in the world, all rolled into one.
In the Dungeons & Dragons setting Points Of Light, all gods have names (Bahamut, Asmodeus, etc...) the notable exception is the neutral goddess of death, who is simply known as The Raven Queen.
In the Planescape setting we get "The Lady of Pain'', ruler of Sigil.
Eberron has this for the gods of the Dark Six, evil gods who were cast out of the "good" pantheon of gods called Sovereign Host: The Devourer, The Fury, The Mockery, The Shadow, The Keeper and The Traveler.
The Lord of Blades, mysterious leader of the Warforged of the Mournlands. Here his namelessness is for a plot hook, so the DM can confer him whatever "true" identity they desire.
In Unknown Armies, members of the Invisible Clergy are meant to abstract representations of ideas about what human beings can be. Consequently, each member is known by the title of what it is representing; for example, known members include The Fool, The Trickster, and The Mother. The Clergy used to be real mortal people with real names, but it is implied that ascension causes them to shed their old identity to become a true Anthropomorphic Personification, and at least one recent ascension actually erased the new member's name from every written record, replacing lost text with her new title: "The Naked Goddess".
In the Warhammer 40,000 mythos, the Eldar do not refer to the Chaos God Slaanesh by name, instead using the referents "She Who Thirsts" or the "Prince of Pleasure", due to their race's connection to the demon-deity in question.
Assassin's Creed II introduces "Those That Came Before", a race of godlike beings that may have been the inspiration for mythical gods.
In Drakengard, the enemies that appear in the path to the fourth ending are called a myriad number of things, "the Grotesqueries" and "the Watchers" being two of them. In the game's sequel, they are called "the Nameless".
Earthworm Jim features Princess What's-Her-Name, but this is a subversion in that her name actually is "What's-Her-Name".
In the first Star Wars: Knights of the Old Republic, if you take up arena-fighting, you'll be given the nickname "The Mysterious Stranger"... This is so they only have to use the one audio track whichever name you choose for yourself at the beginning.
Jade Empire, from the same folks, uses the same convention, though in that case you get your choice of a few stage names. The Arena promoter throws in a Shout-Out to Knights of the Old Republic, referring to you when you first meet him as a "mysterious stranger."
In Mafia, there is a cutscene in which the main character refers to his wife and daughter as "Sarah and the kid", despite the fact that the daughter is a couple of years old and thus should have a name, and that the character he talks to should know the name of the daughter already and thus understand who is being referred to when the name is mentioned.
The Half-Life series has "The G-Man", who is only named according to Word of God; within the games themselves he is unnamed. And even "The G-Man" is just a vague nickname; a colloquialism meaning "Government Man".
A parody in Ratchet & Clank: Going Commando. When Ratchet first enters the arena, he is known only as "This!...Guy...". In the second Arena, Ratchet is named, Clank then takes up the "This Guy" mantle.
Nale: Another one? Good gods, man, that's eleven so far who Must Not Be Named. Not to mention the four who Must Not Be Looked At, the two who Must Not Be Spoken To, and the one who Must Not Be Toilet-Trained.
Also used several times among the villains, with the Creature in the Darkness, Redcloak, his brother Right-Eye, their deity "The Dark One"...
In 8-Bit Theater, there are the Other Warriors, a rival group to the main characters, the Light Warriors. Sarda the Sage is also known as "The Wizard Who Did It." Not to mention the heroes themselves; The black mage, white mage, thief, fighter, red mage, and black belt are called Black Mage, White Mage, Thief, Fighter, Red Mage, and Black Belt respectively. Technically, these are actually their names.
Parodied in the Torg Potter parodies, where Torg Potter is known as "The Lastnameless One", his nemesis as "You Probably Don't Know Who", and the explanation for all this is found in the "The Story We Can't Tell".
The demon K'Z'K gets called "The Vowelless" as well as simply "The End". Most people can't pronounce his name anyway...
In Questionable Content, there is a girl (mainly used as filler art) known simply as "Sweet-Tits", much to her resentment, although it is implied she does have a real name.
Cow and Chicken, had a character called "The Red Guy"—at least in the credits; in the episodes he had various names that all seemed to refer to the fact that he wasn't wearing any pants. Once, during a brief, standalone scene where he addresses the audience directly, he actually refers to himself as "The Red Guy".
Futurama had the one-shot 80's-guy character "That Guy".
And of course "I am The Man With No Name... Zapp Brannigan at your service!"
Word of God says "That Guy" is named Steve Castle, but it was never mentioned during the show.
In The Simpsons, many characters lived without names and were referred to in the scripts as "The comic book guy", "The squeaky-voiced teen", etc.
Occasionally they would receive names later when they became more important; Comic Book Guy became Jeff Albertson, for instance.
Whether or not these names stick is another story. Everyone calls Capitan Mc Allister "the sea captain," even though he was named in his first appearance!
It's common in some religious traditions to either not refer directly to The Devil, or at least to not speak the name "Satan" or something similar. Instead demons are just collectively "The Enemy", or "evil spirits".
Similarly, Jews are not supposed to say the name of God, substituting a word such as Adonai (my Lord) instead. The way in which this was written in antiquity (conflating the consonants YHWH with the vowels of Adonai) has caused much scholarly head-scratching as to what the name of God was actually supposed to be.
In some regions of northern Europe (such as Scandinavia) it was once considered such bad luck to say a bear's true name that today, we aren't quite sure what the word in the language was; "bear" itself was such a euphemism.