The name of the man who murdered Kiriko's fiancé in 20th Century Boys is never given, despite appearing in multiple volumes, being part of one volumes climax and said climax having Kenji outright ask what his name is. At best, the character profiles at the start of Volume 19 call him "The Killer".
The male Survey Corps member with the goggles from Attack on Titan was never given a name or title, he's simply well known as "Goggles".
The main character from the Ayakashi: Samurai Horror Tales Bakeneko arc and its spin-off anime Mononoke is known only as the Medicine Man. His real name, if he even has one, is never given. None of the other characters seem to be bothered by this.
Azumanga Daioh: While she was in most of the first volume (American version), Mizuhara Koyomi goes entirely unnamed until Azuma spends a whole strip on it: three classmates call her 'Yomi', and the teacher gives out the full name. Partway through Volume 2.
In Battle Spirits Shonen Toppa Bashin, it's implied that in Smile's case, this isn't his actual name. Unfortunately, his actual name is never mentioned. In the manga, it's Abaddon.
The Count from Berserk is the only major character in the series without a name. Nobody, even his relatives, ever refers to him with his given name. Also, the child who is highly insinuated to be Guts and Casca's child in some spiritual form but remains nameless due in part because he is mute and because he was never properly given a name upon his "birth." So we just call him "Guska."
Joker (and presumably the rest of the performers in Noah's Ark) from Black Butler. It's actually played as a Tear Jerker after his death, as he has no name because he never had any family to care for him but the (now dead) Circus members.
In Bloom Into You, Sayaka's ex-girlfriend is never named; she simply calls the older girl "Senpai." The same goes for the boy who confessed to Yuu a month before the first chapter and ended up getting rejected.
A Certain Magical Index has a character only referred to as "The girl in the dress". Many, many years after her introduction, her name was finally revealed as Kaibi Gokusai.
C.C. and V.V. from Code Geass. C.C. does have a real name, but after Lelouch learns it he keeps calling her C.C., apparently by her own preference. After she loses all her memories and mentally reverts to the age of ten it gets a bit awkward since Lelouch never calls her using anything except "you". V.V. also presumably has a real name, since he is Emperor Charles' twin brother and, therefore, Lelouch's uncle. Both names are the The Un-Reveal, despite Season 1 having implied that C.C.'s real name was in some way important.
Cowboy Bebop gives us Vicious. The story plays more on what he does in the present more than who he is. We're certainly given no indications that it's not his real name — even his girlfriend called him that.
Played for laughs with Hokuto's lackey from Cromartie High School. The running gag throughout the whole series is that he gets cut off before he can say what it is. The background and author notes in the manga finally does reveal his name to the reader, but the whole cast of the series admits that it's better that he just continues to go by "Hokuto's Lackey" because they've built up their friendships and familiarities with him around it. Learning his name would be a rather jarring change to that relationship.
We still don't know Hei from Darker Than Black's real name, even though he's the hero. He has a civilian alias, but that's probably completely unrelated to his actual name, and he typically goes by a Code Name instead.
The same is true for virtually every Contractor in the show.
L in Death Note orders the police officers aiding him to call him Ryuzaki, but his real name is never shown. In a book of extras entitled "How to Read", his name is revealed to be L Lawliet. If you watch the live action movie L: change the WorLd you see his name written in the death note. Also, you can just barely catch that his first name is just "L" in the second movie.
In Delicious in Dungeon, three characters have been introduced but not named yet: Zon's son, Zon's little sister and the lord of the Island.
While not a major character by any stretch of the imagination, Tomoki's older brother in Digimon Frontier was never named in the Japanese version; both Tomoki and their parents simply call him "oniichan," or "big brother," which isn't uncommon in Japanese families. However, it would have sounded strange to the American target audience, so, in a fit of Woolseyism, the dub writers named him Yutaka. "Yutaka" is an anagram of "Takuya," The Hero, and he and Tomoki have sort of adopted each other as replacements for their actual brothers.
As is the Kami-sama of Dragon Ball. When he re-fuses with Piccolo, the resulting whole person notes that he can't even remember what his name was before he split into good and evil, so he decides to keep calling himself Piccolo.
Androids 17 and 18 are in a similar situation. They are actually cyborgs, humans who were "remodeled," so they do have real names, but since they can't remember them, it's never revealed what they are, and they just go by their numbers. However, Akira Toriyama eventually revealed their real names in the Q&A section for the Full Color manga: Lapis and Lazuli.
In Dr. Slump King Nikochan's servant, the policeman with a Stormtrooper helmet and the young biker who appears at the end (who is also The Faceless) are never named.
Some characters from Elfen Lied are unnamed. Two of them are referred as "The Unknown Man" and "The Agent" by the fans.
Isobe doesn't have a name in the anime version. And a completely different character design.
One of the (sort-of) antagonists in Excel Saga is known only as That Man. In the last episode (which intentionally never aired due to insanely offensive content) he's revealed to be part of a cabal of six people, all of which look identical to him, and are named That Man Over Here, That Man Over There, This Man, This Man Over Here, and This Man Over There.
The Alphabet Team in From Eroica with Love. Each one is assigned a code letter, and we never find out what their real names are. Lampshaded at one point by an antagonist, who claims that the practice is dehumanizing.
Also Führer Kingnote His first name is actually "King". Bradley aka Wrath. Having been raised from a baby solely for the purpose of becoming a Homunculus, he has no idea about his birth name. The identity of 'King Bradley' was given to him purely for appearances.
Edward's and Winry's children haven't been given official names.
The name of Rosé's child in the 2003 anime was never confirmed despite him appearing several times as an infant and once as a toddler.
Makubex from Get Backers. He was found in a bag that had "Makube" written on it, and has no idea what his actual name is. The "X" was added later to represent the unknown. There's also the Specialist, a white-haired, red-eyed little girl who shows up from time to time, carrying a white rabbit doll and telling Akabane to kill people the Brain Trust doesn't like. Her name is later revealed (by a dying man, no less) to be Makube!
Ghost in the Shell: Stand Alone Complex: Only two of the main characters (Section 9 chief Daisuke Aramaki and Major Motoko Kusanagi (which itself has been described as an "obvious pseudonym" by the author and justified by Motoko's past)) have full names, with every other member of Section 9 going by one name only.
The last episode of the first season reveals that these are just codename aliases with the exception of Togusa, who uses his real family name, presumably because it would get awkward if his wife learned that his coworkers call him by a different name, especially since as far as she knows, he is an employee of a security firm, not a Public Security agent. The Major implies having erased her past, and possibly even parts of her own memories for reasons unknown; in the 2nd Gig she reveals regretfully that she has forgotten her real name.
Played completely straight with the Minister of Home Affairs. A character who has shown up numerous times in meetings with Aramaki, has a decent amount of dialogue, and is a key figure in allowing Section 9 to exist, has no name. Not even in the manga is he given a name. The fanbase has dubbed him "Jabba the Home Affairs Minister" due to his fat, wrinkled Gonk face.
Every single character in Goblin Slayer is only ever referred to by some kind of title, something to do with their race, gender, skills, and/or occupation, the most prominent example being the titular Goblin Slayer himself. They presumably do have real names, as it's part of the adventurer application, but nobody ever uses them from the audience's perspective. It gets so ridiculous that some characters are only given awkward titles in the narration itself, such as the the busty farm girl naturally known only as Cow Girl.
In Gregory Horror Show, we never find out what either of the guests' names are. Ever. Neither of them give it out, and the only other character who might know it (since they'd have to sign into the hotel anyway) only addresses them by a Term of Endangerment. All official material only refers to them as "Guest" and "Second Guest."
The protagonists of Gunjo, who are known simply as the Blonde and the Brunette.
One of Mohiro Kitoh's collections of stories, Hallucination From The Womb, has practically no named character. Maybe one or two receive names, and none of them are full names. Even the recurring characters are only referred to as "Female Controller" and "Male Controller."
Kyon, the Computer Club President, and Kyon's sister — Kyon bemoans his stupid nickname but never says his real name (his school introduction is cut off). Even his sister's image song had to be titled as "Kyon no Imouto-san" or "Kyon's Little Sister". When Emiri Kimidori is about to say the president's name, it is covered up by a sudden cut-off to a random cat meowing.
So far, the closest hint to what Kyon's real name might be was Sasaki from the ninth novel saying that it was distinguished and almost regal-sounding. Doesn't really help that much.
Also in the ninth novel there is also another character, a rival time-traveler from the future, who seems to prefer this, actively showing disdain for even the existence of names. For the sake of reference, he suggests that they call him Fujiwara. Kyon prefers to just call him The Sneering Bastard.
Most of the characters of Humanity Has Declined are not given names. The protagonist is listed in the end credits as "Watashi", so fans tend to call her Heroine or Mediator. Most of the other characters are likewise referred to by their job/title: her assistant is only ever called Assistant, her grandfather Grandfather, and so on. Y is most likely a pseudonym (English letters are often used in Japanese to obscure names, like A-ko meaning "Girl A"). The only characters with confirmed names are P-ko and O-taro, or more appropriately Pioneer and Voyager.
In Hunter × Hunter the Chimera Ant King abandoned his dying mother the Queen before she could name him. One of Netero's subordinates heard her name the King 'Meryem' before she died and relayed that information to Netero. Netero goaded the King into a fight by offering to tell him his name if he could get Netero to admit defeat. By this point in his Character Development, the King had become human enough to be bothered by his lack of a name.
Due in part to dying before the beginning of the series (her only appearance being a brief flashback), Dio's Mother is never given a name.
Poco's Sister is never named during her time onscreen.
In Battle Tendency, Santana's actual name is never given, with Santana being a name given to him by Stroheim. However, he's later referred to as Santana by Kars, despite Kars being one of the few people who would know his real name, so perhaps Stroheim was actually right.
What the "J" in J. Geil's name stands for is never revealed. Given the "J" in the real J. Geils stands for "John", it's most likely that.
A number of minor villains of the Part were never given names in the manga, with their names only given in supplementary materials. These include Tower of Gray's User (Gray Fly), Strength's User (Forever), Yellow Temperance's User (Rubber Soul), Wheel of Fortune's User (ZZ), The Sun's User (Arabia Fats), and Death Thirteen's User (Mannish Boy).
Josuke's Savior only appears briefly in a flashback, and as a result never being given an actual name.
The names of the two rats with the Stand, Ratt, are never revealed, with the name, "Bug-Eaten", given to one of them being a name made up by Jotaro. That is, of course, if they even had actual names at all.
According to the man himself, Toyohiro Kanedaichi is not his real name. Assuming he's telling the truth, his actual name is never given.
Giorno's Mother only makes a brief appearance in a flashback, never being given a name as a result.
Giorno's Hero only appears in a flashback, and as a result is never given an actual name.
The turtle whose Stand Team Bucciarati use as a base of operation is never given a name in the manga, with his character file stating that "no one bothered giving him a name". Supplementary materials, as well as adaptations of the Part and any future works involving the turtle would give him the name Coco Jumbo.
None of the Eleven Riders from Steel Ball Run are ever given names, leading them to often being called the "Eleven Nameless Men" by fans.
An odd example for Kashiwagi's boyfriend in Kaguya-sama: Love is War, as not only is he a Recurring Character but he even appeared before Kashiwagi. But we haven't gotten his name at all, the extras only list him as Kashiwagi's boyfriend and nothing else. This changes in Chapter 109, when Maki finally reveals his given name (with the Narrator stating that after 109 chapters, we finally learn his name). Shirogane and Ishigami lose focus of the conversation due to this fact. And his last name isn't given until Chapter 180.
Trowa Barton from Mobile Suit Gundam Wing was separated from his family as a baby and raised by a band of mercenaries, who never named him. He remains nameless his entire life until the eve of Operation Meteor, when he lifts the moniker of the man originally trained to pilot the Gundam Heavyarms. After Endless Waltz, he considers himself nameless once more, until his friends convince him to keep it.
Of course, early on in the show, it's demonstrated that he still hasn't fully accepted the new name:
Trowa: Battle Record 001, pilot's name...let's go with Trowa. Trowa: I don't have a name. If you must call me something, call me Trowa Barton.
Heero Yuy's name is also just an alias given to him by Doctor J. What his given name was (if he even had one) is never revealed.
Mobile Suit Gundam SEED Astray has one pilot whose name is never revealed. If he even has one. The closest we get to one is the error code given when they try to access his records: ND-HE ("No Data — HIGH ERROR"). He's eventually revealed to be a clone of Astray's Gai Murakumo.
Monster: Johan Liebert is simply one of many aliases he happened to be using when he met Tenma. His birth name is never given.
Nobody besides Mr Ando from Mori no Ando is given a name, referring to them as "the wasp", etc.
Mushoku Tensei begins with the story of the protagonist just before his death as a Japanese man and reincarnation as Rudeus Greyray. His Japanese name is never revealed and the one time it is spoke by his future self the word is censored.
This was revealed to be the case with Tobi. The one notable name he went by was a lie to lend him credibility; he prefers to remain nameless and focus only on his end-game. On chapter cover simply refereed to him as "The Masked Man". He's actually Obito Uchiha.
Each of the bijuu bears a name given to them by the Sage of Six Ways but because of the general belief that they're little more than mindless energy, few humans bother to learn a name beyond their title. As of Chapter 572, the names of the nine Tailed Beasts have been revealed, most notably Kurama (Nine-Tails) and Son Goku (Four Tails). It is worth noting that Shukaku is the real name of the One Tail so it is the only Bijuu actually referred by real name before this event.
This is just one of the many reasons that Bijuu hate humans: instead of calling thinking, indeed very intelligent animals by their proper names, they've assigned them numbers. Nine-Tails seems annoyed that Naruto never even took in the possibility that he had a name and Four-Tails is outright furious.
Interestingly, the Third Kazekage and the Third Mizukage are the only known Kage to not given names, despite other Kage being given names either on screen/panel or in the databooks.
Yamato and Sai never revealed their real names, or indeed if they ever had real names rather than just a series of code names. They end up adopting the names they were introduced with, for Yamato simply because he preferred it to any of the other names he's gone by and Sai because it was the name he was using when he was freed from ROOT. Out-of-universe, of course, the reason is that those were the names fans knew them by.
Hinata and Hanabi's mother, who is an anime-exclusive character, has never had her name revealed.
In One Piece despite literally hundreds of chapters going by, the Five Elder Stars of World Government deliberately remained unnamed. Fans and wikis call each of them the scarred one, the tall bearded one, the forehead birthmark one, the bald one with sword and young blonde one.
Done brilliantly in the Mystery Dungeon anime specials, in which the protagonists are only referred to by the Pokémon they have turned into (Squirtle and Piplup, respectively). In the games, the player's partner asks for their name and they go by thus in the games, rather then their species name. They go so far as to keep calling the protagonist Piplup in the third special, which is well after the point in the story where, according to the games, the player's true name is a major plot point.
Awkward is more like it. It seems like their names are "Squirtle" and "Piplup", or they've gone through some mega amnesia compared to the games.
Not likely. Upon waking up and meeting their partners for the first time, they seem confused to be addressed as "Squirtle" and "Piplup".
In Ranma ½, the Jusenkyo Guide (whose daughter IS named,) the Gambling King, and the Dojo Destroyer.
Obviously 'Kami-sama' of Saiyuki is not actually NAMED thus. He just gets called that. His real name is never known.
Interestingly used in Samurai X: Trust and Betrayal where Kenshin explains to Tomoe that he doesn't hesitate to kill his enemies because he does not know them, and if he knew their names it would be harder for him to kill them, sometime later we see at least a pair of mooks yelling their names before confronting him, to which Kenshin answers "shut up and die anonymously"
In Sazanka, Tatsuki and Aoi's mutual friend is never referred to by name in the story; when Aoi once complains about "her," the girl in question's face is shown to clarify that Aoi's referring to her. While bonus pages reveal the surnames of the entire cast, which are never used in the story, the girl in question is simply called "Friend A."
From Shaman King: Horo-Horo's real name is Horokeu Usui (Horokeu is Ainu for "Japanese Wolf"). This is never ever mentioned on the anime, but had a whole special secret connotation in the manga.
Free from Soul Eater. Having been the prisoner of witches, his captors even took his name from him and merely called him "Devil's Eye". When Medusa freed him, she basically told him "He's free," and the simple-minded werewolf ran with it (Free was anything but at that point, being indebted to the show's Magnificent Bastard).
Spotted Flower characters, the protagonists are a Husband and a Wife, and later the Wife's Grandmother join in.
In Sword of the Stranger, the closest thing the ronin gives for a name is "Nameless Red Devil." Kotaro even starts calling him Nanashi, which translates directly to "Nameless".note Nanashi is to Japanese as Anonymous is to English
The protagonist of The Tatami Galaxy is never named. Ozu, furthermore, is only ever known as such.
LegatoBluesummers of Trigun takes pains to introduce himself dramatically the first time he meets the protagonist. In the manga, this is revealed to be because he apparently chose that name himself, after Knives saved him from being raped to death at the age of...somewhere between eight and thirteen, spared him, and asked his name. So far as he knew, he'd never been given one.
The titular character of The Walking Man is never given a name at any point, but considering the narrative's laser focus on the immediate experience, his name or identity aren't particularly relevant to the story.
The Wallflower gives us Auntie, the prince, and (in the manga) Ranmaru's fiance.
Yuko Ichihara from ×××HOLiC never reveals her true name, as that would give others power over her and so only uses a pseudonym.
In Yona of the Dawn, the current seiryuu is only referred to by his title in his village. His mother killed herself after giving birth to him, and the villagers fear and shun him. When Yona finds him, she gives him a name, Shin-ah.
In Yu-Gi-Oh!, the Spirit of the Puzzle spends most of the series without a name of his own. Instead, he is referred to by the name of his vessel, Yugi, or by his title. The manga character profile pages call him "Dark Yugi" or "Yu-Gi-Oh". The NA dub anime characters and story information packets call him "Yami Yugi." The character's real name is Atem. The name is historically significant, as in real life this Pharaoh was so notorious efforts were made then to strike his name from historical record.
The Exodia-using Rare Hunter in the Battle City arc was never given a name (fans tend to call him Seeker but that isn't official.) In the manga version, Yugi asked what his name was, but then quickly decided he didn't want to know and told him to forget it.
Yuuutsu-kun to Succubus-san: The characters aren't given proper names until Chapter 34. In fact, Metasuke is the fourth character introduced but the first one to be formally named. In Chapter 34, however, Eru lampshades it when learns Sakuma's chosen alias, at which point she gives her own full name, and Yuu reminds them of his name, in case anyone forgot or didn't know.