Adolf has three title characters: Adolf Kaufman, German diplomat's kid; Adolf Kamil, the son of a German baker, and that one.
ARIA: The animation features Alicia and Alice which are the same name (Italian/English). It never was brought up.
School Rumble has the Japanese Delinquent Kenji Harima (or, in the Japanese surname-first style, "Harima Kenji") and the American exchange student Harry McKenzie — names which, when pronounced with a Japanese accent, sound nearly identical. Naturally, one of them is often confused for the other in conversation, and Hilarity Ensues.
Also, one of the main girls is called "Suou", she briefly dates a boy called "Asou", nobody seemed to care how similar-sounding their names where.
Rave Master has two characters named Musica, because the author liked the name and couldn't decide which of the concepts to use. Also, there were two main characters named Gale; one the main character's father and one the primary antagonist for the first half of the series. When the latter was named, he was initially assumed to be the former.
Nana's two main characters are Nana Komatsu and Nana Osaki. "Nana" as in "Seven", that is. One promptly nicknames the other "Hachi" (Which can mean Eight, and is also based on the famous dog Hachiko due to her clingy personality.)
And later on there are two Misatos and two Rens.
In Gantz there are Kei Kurono and Kei Kishimoto. Less confusing than other examples by the fact that Kurono is a lecherous teen boy, and Kishimoto is a sweet but depressive busty girl. Not to mention that each one is of opposite gender.
Kamichama Karin has Kujyou Himeka and Karasuma Himeka. Their names are written with different kanji, though.
They're two parts of the same person so it doesn't really count.
Dennou Coil has two characters with same-sounding given names, Okonogi Yuko and Amasawa Yuko. They get different nicknames (Yasako and Isako) quickly.
Gakuen Alice has two characters with the same name: Misaki, a teacher and Misaki Harada, a middle school student, both of which are major characters.
CLANNAD has a main character by the name of Tomoya with a primary female character by the name of Tomoyo. Only a one-letter difference.
And also Tomo, her half sister in the sort of sequel.
Koi Koi 7 has two characters named Yayoi Asuka. One is a pink-haired ditz, the other is an eyepatch-wearing silver-haired ruthless type. Once the latter Yayoi is rebooted, she then goes by "Gantai-chan" (literally "Eyepatch-chan").
Get Backers has a Kaoru Haruki, a Haruki Emishi and a Kaoru Ujiie.
In an episode of Excel♥Saga, the heroine Excel puts up fliers around the city in an effort to find her missing partner Hyatt. In the next episode, one of the fliers is found by two girls named Mikago Hyatt and Excel Kobayashi, who misunderstand and think they're wanted for auditions for a band. These two show up again in another episode as guests on a TV show to sing the Excel Saga theme song.
Naru Taru has the major character Akira Sakura, and minor characters Aki Sato and Aki Honda. None of them are ever mixed up with one another, and it's really just as well - especially given Aki Honda's nature.
The CLAMP metaseries does this very confusingly. There's Syaoran and Sakura, their son, Syaoran, his girlfriend, Sakura, and the latter two's clones, Syaoran and Sakura. Played with in that everyone with the same name looks exactly alike. Except for the Syaoran that DOESN'T look alike them, Li Syaoran AKA Watanuki Kimihiro.
Making that worse, the latter pair ARE the aforementioned parents. And if we take them at their word that the Tsubasa multiverse includes all Clamp universes, there's also Cardcaptor's Sakura and Syaoran. Head hurting yet?
But oh it gets better! The non-clone Syaoran and Sakura, who imply several times during the series that their names are pseudonymous are in the final chapter both revealed to be named Tsubasa.
And now there's Sakura in their new manga, Gate 7, who doesn't seem to have anything in common with any of their other Sakuras.
Which Pokémon trainer do you suppose Ash Ketchum respects more? Aaron, the Elite Four member and bug specialist? Or Aaron, the ancient aura-wielding knight whose Lucario he befriended? And don't forget about Drake and Drake, from the Orange Islands or the Hoenn League, respectively. Or Flint, Brock's father, and Flint, a member of the Sinnoh Elite Four and rival to Volkner. Or Bianca, the girl who was frequently impersonated by Latias, and Bianca, the ditzy female rival in Unova.
In all four cases, the reason for this is because one character is originally from the games and one is anime-exclusive. Also, in all four of the above cases, the anime character debuted a generation (or more) before the game character.
In the French games, Brock and Steven are both called Pierre, the latter also being given the last name Rochard. Probably just to avoid confusion, when Steven/Pierre Rochard shows up as a guest star in HGSS, he doesn't give his name.
The (in-game) granddaughter of Professor Oak and an (anime-only) elder sister of Misty are both named Daisy. This time, they're Same-Gen, though the former wasn't originally named in the original games.
Gary's sister, in the anime-based manga The Electric Tale of Pikachu, has her name inexplicably changed to May, which happens to be the name of the female protagonist in Pokémon Ruby and Sapphire... and the corresponding Anime seasons... and the sequel manga based on those seasons.
Misty's sister happens to have a rare Japanese violation, though, in this case and in keeping with the pattern, she's first: she shares her Japanese name with one of the Kimono sistersnote Ironically, the one Misty herself befriends: Sakura.note The Anime kept the Japanese game names, but the English (and German) games themselves replaced the names with others for some reason; there, she's Sayo (Keiko)
The games reuse names frequently as well - even those of Gym Leaders. For example, in Sinnoh there is a Parasol Lady named Sabrina. Though since Sabrina the Gym Leader does not appear in Sinnoh, there is no confusion.
Given that the show usually has a new character every episode foronly a single episode, this trope comes into play very frequently, mostly due to writers forgetting or not caring about previous characters, since it's been years since we saw them. Even amongst anime-exclusive characters. The first of these was Harrison, who appeared in Episode 265, sharing a name with Harrison, who appeared in Episode 216. Others have appeared since then.
It's actually discussed about Max and Max in Episode 323, though unlike the above this was intentional, as the two look almost exactly like each other. Also, unlike most of the above, they're both named Masato in the Japanese as well.note The 5 aforementioned Game vs Anime cases are, in order: Ryo vs. Arlon, Genji vs. Yuji, Oba vs. Muno, Bel vs. Kanon, and (the same-gen example) Nanami vs Sakura Plus, like Harrison and Harrison,note aka: Hazuki (265) and Harizo (216),they're both Anime-Only.
Incidentally, Stephannote Kenyan is not a violation as it's also a different spelling than Hoenn's Stevennote Daigo. However, the latter did have a CotD with the same name in the dubnote but, again, not in the Japanese: Saiga which, again, came in an earlier generation: specifically Johto.
Detective Conan uses this in some mysteries for added... mystery. Not to mention they have a huge list of minor characters, so every once in awhile names are going to HAVE to cross with each other. For example, the series' character sheet listed two one-shot chatacters called Hiroki, and there's at least one more not listed there.
Hilariously used in a recent case where one suspect was also named Kudo Shinchi (aka the main character.) Then he was promptly murdered.Status Quo Is God
In Arata Kangatari, both main characters are named Arata. They're generally distinguished between each other by refering to The Hero by his last name, Hinohara. In Japanese, the reader can distinguish between the two in the dialogue by whether or not "Arata" is written with kana or kanji; Hinohara's name is written with the latter, and any character in either world that knows about the nature of the switch will have their dialogue use the correct kanji/kana when referring their respective Arata.
The sheer number of characters in Prince of Tennis means that names end up being repeated. There are three Hiroshis (Wakato, Yagyuu and Chinen), two Hikarus (Amane and Zaizen), two Kentarous (Aoi and Minami) and so on. Luckily the majority of them are on a Last Name Basis. (Note also that many of these names are homophones, but written with different kanji.)
Monster has two Martins, two Adolfs, and two Karls. There are also three different Ottos, although one is a story-book character within the series.
While the Naruto manga alone, as a sheer result of a huge-ass cast with databooks giving practically every character seen for even a moment a name, has only one exception (both one of Danzo's bodyguards and the host of the 7-tailed beast are named "Fu," both of whom you can use in Naruto Shippuden: Ultimate Ninja Storm 3), if you go multi-media there are several characters with repeated names. For example, both Sasori's puppet armor (and thus the person he made it from) and the Big Bad of the sixth movie/third Shippuden movie are named "Hiruko", a subject of Orochimaru's cursed seal experiments and the main villain of the Three Tails filler arc are named "Guren", a minor filler character is named "Yagura", which later turned out the name of the former Three Tailed beast host and the Fourth Mizukage, and both there are two unrelated Fuma Clans (one from a filler arc, one mentioned to be where Pain's first Animal Path came from). However, the Japanese spellings of these characters names are different. There was a filler character called Jiroubo in addition to the canon Jiroubo. Also Matsuri was used as the name of Gaara's student/fangirl and a girl in Konohamaru's academy class. In the anime, Sabu for some reason had his name changed to Kin, which was the name of one of the Sound Village genin.
In Eyeshield 21, the Kyoshin Poseidons have two Hiroshis on their team (Hiroshi Ohira and Hiroshi Onishi).
Mai-Otome has two recurring characters named Mikoto, one an Expy of the Mai-HiME character of the same name, the other is Queen Mashiro's pet cat. There actually is a connection between them.
One Piece has a couple people named John: Zoro's old friend and fellow Bounty Hunter Johnny, Marine John Giant, one of the Zombie Generals of Thriller Bark was named Captain John, and the G8 filler arc features a Marine Vice Admiral named Johnathan.
Ace's cover story, where he's hunting down Blackbeard (real name Marshall D. Teach), once has him run into a similar looking but completely unrelated Dr. Blackbeard, who he mistook for Teach, kicked in the face, and was throw into a river by the townsfolk this angered.
It has also has two Jones's - Hody Jones and Davy Jones himself.
Scotch is the name of both the pirate X Drake battles on one of Kaido's islands as well as one of the Yeti Cool Brothers.
If you take Filler into consideration, certain filler characters share names with significant canon characters, such as the filler Marine Drake and X Drake, a filler pirate Bonney and Jewelry Bonney, and so on.
Holding the record for One Piece, there are four characters named Billy: A pirate in Loguetown, a bandit in Alabasta, a cook working for the Marines, and an electric bird in Merveille. All of them are non-canon, meaning the manga could produce an official Billy at any moment.
One Piece has also several characters called "Marie" or similar (the nurse Marie, Boa "Mari" Marigold, the housewife Maria Negikuma and the diva Maria Napole) and "Catherine" or similar (Baroque Works agent Miss Catherine, pirate Catarina Devon and waitress Gatherine).
Digimon has pairs of monsters with the same names that are distinguished by their levels—Rapidmon (Armor) from the Digimon 02 movie and Rapidmon (Ultimate) from Digimon Tamers, and Kumamon (Rookie), originally Bearmon, from Digimon World 3 and Kumamon (Hybrid), originally Chakkumon, from Digimon Frontier. When two digimon are different enough but of the same name and level, fans list the year the new one was introduced to draw a distinction such Adventure and Adventure 02s Agumon and Savers' Agumon(2006).
Some are fixed by Dub Name Change. There are two digimon named Deathmon who are completely unrelated. The dub names the new one Ghoulmon to distinguish them. Then there are two digimon named Deathmeramon, who are only superficially related. The Dub changes the new one to Skullmeramon.The New Metalgreymon may get the same treatment.
Miyuki has two girls named Miyuki. Both are love interests for the protagonist. One of them is his stepsister. Confusion between the two does become a bit of a plot point.
YuYu Hakusho has Kurama's little stepbrother Shuuichi, which is same as Kurama's human name.
Hayate the Combat Butler's Izumi and Isumi, are mixed up by fans often, but haven't yet had the issue within the story. Until the story, they apparently had little interaction and even their social groups are separated, so it might never come up.
Most of the male characters have similar-sounding names, but given the Unwanted Harem style of the story, they're never likely to come to even meet.
Ghost Sweeper Mikami has two Orihime; one's a weaver for spirits and gods, the other is the legendary star goddess whose doomed love affair the Tanabata festival celebrates. Still, since they're both practically one-shots (the former, after her first appearance, is only referred to by name once or twice afterwards, and the latter is a one-shot), there's no risk of confusion whatsoever.
Bakuman。 has two Hattoris, who are apparently not related. Akira Hattori is the main characters' editor, while Yujirou Hattori is Eiji Nizuma and Shinta Fukuda's editor. Yujirou is typically referred to by his first name to keep them separate, and when he calls Akira by his last name, Akira thinks to himself that he has the same last name.
There's only one Haruhi. When Kyon asks about her in the movie Disappearance, only one character can remember a Haruhi from years ago. This is a name so common in Japan that it doesn't get a One Mario Limit in spite of the series popularity, but in her world, she really is that special.
This just might be justified by what Haruhi is, so she wouldn't want anyone else to share her name.
In Sketchbook, cat lover Sora encounters a new stray cat and decides to call him Haa. Her brother then points out that there's already a cat with that name around, so she comes up with a new one. She also names all Calico's "Mike", after the Japanese name for Calico "Mikeneko", resulting in "Mike the 2nd", "Mike the 3rd", etc. Eventually neither Sora, nor the cats themselves can remember who's who.
In Puella Magi Madoka Magica, there's Kyouko and Kyousuke, both recurring characters. This may not look identical, but since "-ko" and "-suke" are gender-specific name suffixes, their name were practically homophonous. So, when a character called 杏子 was introduced after Kyousuke, people thought her name would be pronounced Anko because of this trope. "Anko" remained Kyouko's Fan Nickname, and you can bet that her name being essentially a feminized version of Sayaka's crush Kyousuke has not gone unnoticed by Kyouko/Sayaka shippers.
Neon Genesis Evangelion oddly has Ikari as the last name for two main characters (father and son) and a secondary character whose first name is Hikari.
Subverted in X/1999. One character is named Seishirou Sakurazuka. Another one is named Seiichirou Aoki- and is referred to as Aoki, probably in order to avoid confusion.
In the Ace Attorney manga, there are two characters named Buck in the English version, one with the last name Montana and one with the last name Wheatley. Their names are both puns; Montana's refers to his buck tooth, while Wheatley's refers to his occupation as president of a buckwheat company.
The Girls Love manga Lonely Wolf, Lonely Sheep revolves around two woman named Kakimoto Imari developing a bond after they meet at a clinic. Their name is written the same way, they were born in the same year, and their birthdays are one day apart.
Read or Die has a character named Maggie who's Drake's daughter. Meanwhile, in sister series Read or Dream, one of the main characters is Maggie Mui. Naturally, when crossover series ROD the TV came out this trope came into effect (Drake even has a double take when Maggie Mui introduces herself.)
Descendantsof Darkness has Hisoka Kurosaki and his dead older half sister also named Hisoka which is quite sad when it is implied that Hisoka's father Nagare seemed to have cared more about his daughter than he did about his son
Hiroko Murosashi and Hiroko "FunaQ" Funakubo. The two never interact, though, as the former is one of Nodoka's kohai from Takatobara Junior High, and the latter is a second-year player from Senriyama who is the coach's niece and Hiroe and Kinue's cousin.
Yoshiko Yasukouchi, a player for Shindoji, and Yoshiko Kainou, a professional mahjong player.
While the viewer knows that Saki and Teru are sisters, many people in universe believe that it's just a coincidence that they happen to have the same last name, since they go to different schools in different prefectures. It also doesn't help that Teru refuses to admit that Saki is her sister.
Played with in Magi - Labyrinth of Magic. Someone tells Aladdin the name of the leader of the local thieves group, which is the same as a friend of his. Aladdin brushes this off as a coincidence, and the person who told him admits that the name is pretty common. Unfortunately...
Mobile Suit Gundam Wing's head writer Katsuyuki Sumizawa seems fond of the name "Catherine", the anime and its related stories contain no less than five different women with that name or variations thereof: the anime has Trowa's adoptive sister Cathy Bloom and Relena's mother Katrina, the prequel manga Episode Zero has Quatre's mother Katherine, and the sequel novel Frozen Teardrop introduces Sally Po's daughter Kathy and Quatre's younger sister Katherine (presumably named for her mother)note There are also Flash Back chapters focusing on a Katrina Peacecraft which may either be Relena's previously-mentioned mother or possibly her grandmother, but which it is remains unclear due to the fact that no English-speaking fans are willing to translate the novel.