There are quite a lot of Servants that have made their debut in this game, and have been greatly loved by the fans.
- Sasaki Kojiro, although originating from the original Fate/stay night, was not planned for any major story appearances before players began to make memes about his being the "Savior of France," thanks to the early story chapter having lots of Rider-type dragon enemies he enjoyed class advantage against and a low rarity that meant everyone had access to him and his Boring, but Practical playstyle. This not only secured him several references in several events to come, he gets a role in Shimousa as the Nameless Saber, serving as the episode's Post-Final Boss.
- Scathach was a huge hit instantly after her reveal and in-game debut. Statistics showed that she made more money than any other Servant ever had before her debut, despite minimal story presence until America. The director even admitted they made her Assassin version the welfare Servant of the 2016 summer event so players could have at least one version of her. She later received another variant, Scathach-Skadi, who created an entirely new metagame (or if you prefer, she revived a metagame that desperately needed help) and is generally seen as one of the most powerful servants in the game. Scathach-Skadi herself would get a variant for the seventh summer event.
- Saint Martha only made an appearance in Orleans as an easily disposed-of brainwashed antagonist along with bit roles in events. But her quirky personality shown through these events and player interactions (basically, anything but the actual story), the implication that she defeated Tarasque with her fists, and her voice actress made her an instant favorite, leading to her getting frequent event cameos, a swimsuit Ruler form, and being on the arcade game's roster as well as being the Deuteragonist for the 4th Christmas Event, where she enters a lucha libre/martial arts tournament as the team's trainer and Charlie Brown from Outta Town substitute, and then being the Santa Servant for the 7th Christmas Event.
- Jeanne Alter was an interesting concept, but in her first appearance in Orleans, her design was simply a Palette Swap and she was merely an Arc Villain. But people found the idea interesting enough that she was brought back for her own event, and her popularity skyrocketed after said Da Vinci event, which fleshed out her characterhow , gave her a new design and animations and made her Promoted to Playable, with players finding her to be the offensive Game-Breaker and her becoming a big money maker as a limited Servant. She's gone on to be a major character in multiple later main stories and events.
- Several Type-Moon staff members have Kintoki pinned as their favorite Servant for the same reason as the fans: he's versatile against bosses and easily cleans up mobs for farming. The Onigashima event had a Rider version of him as the free Servant because he was so popular, and each year has an event for himself and a long string of related servants, more of whom are introduced each year thanks to their connection to him. And his Rider form is a Game-Breaker as well, so he's become even more popular. He now has a Day In The Lime Light during Part 2's Chapter 5.5, Hell Realm Mandala: Heian-kyō - "Flash of Roaring Thunder"
- The Japanese fandom really loves Shuten-douji, introduced in the Rashomon event, for her seductive, drunk, and teasing voice, provided by a very popular voice actress. Her pairing with Kintoki from the same event is one of the more popular pairings among the fanbase, and notably one of the few pairings to actually appear in official merchandise. Her popularity goes to the extent of the Halloween 2018 event, where a Caster version of her is given out as a welfare event servant, and a second iteration of her as a Saber in a main story event.
- Altria Lancer Alter is one of the most popular of the already-popular Altria variants, which is rather disproportionate when she's also notorious for being Out of Focus: she was barely involved in the London storyline that introduced her, and her only other appearances have mostly been dominated by jokes about her boobs. Yet she has a strong fan following not just for her Ms. Fanservice appearance (which is shown off very well on certain Craft Essences), but also the very limited lore about her depicting her as a Lawful Good Alter who's merely a Hero with Bad Publicity, as well as a potential counterpoint to the notoriously fearsome Lion King. The fact that her kit pretty much codified the Buster Crit playstyle also earns her a lot of love, as does her notoriously weird but oddly charming Crack Pairing with Nightingale, thanks to her playing the Ox King during the Journey to the West event.
- Ereshkigal exploded in popularity upon her debut in Babylonia, even though she wasn't even a playable Servant at the time of the chapter's release and not even having her own unique character sprites (she turns into a Massive Ghost before her boss battle). This is most likely due to a combination of her own possession of Rin like Ishtar (and taking the form of a good-looking Palette Swap of Rin), her endearing interactions with the Protagonist while pretending to be her sister, and her Heroic Sacrifice that greatly buffs the player's Servants to the point where defeating Tiamat is much easier. Her popularity with the players eventually lead to her becoming the featured SSR of the Christmas 2017 event.
- Leonidas is merely a 2* Servant, but he stands amongst the most popular of those people despite his only main story appearance being as a side-character in the Babylonia chapter (albeit a really memorable one). People really liked his extreme tanking utility even for a low rated Servant, being manly and having tons of Shout Outs to a more widespread version of Leonidas, including the yell "THIS IS SPARTA!". His Hidden Depths of being actually intelligent for Spartan standards and being scared shitless of ghosts and Mash fangirling about him also adds up to his charm.
- Quite a large proportion of the fanbase loves Ushiwakamaru thanks to her personality, her voice actress and generally being a very useful Rider overall, especially for the rarity (although her identity being the younger version of the ever-romanticized Minamoto no Yoshitsune certainly helps). Her even more Adorkable portrayal in the Babylonia anime, her budding friendship with the protagonist, and her Dying Moment of Awesome fighting against Gorgon/Tiamat made her even more popular. Despite this, her only main story appearance was in the Babylonia chapter, where she played a similar role to the aforementioned Leonidas, although she is a perennial figure in many story events, which might've led to her role in Babylonia to begin with. Because of this, there are many perks that Ushiwakamaru enjoys: A swimsuit Assassin variant, an Avenger variant (complete with Hotter and Sexier design) under the name of one of her past rivals (Taira no Kagekiyo), and being the first FGO-exclusive Servant (a 3-Star one at that!) to become a Guest Fighter in Melty Blood Type Lumina.
- During the Solomon chapter, the Fourth Demon Pillar, Barbatos, became the primary target of pretty much every player due to his highly sought after material drops, despite otherwise differing little from the other Pillars in characterization. This had the side-effect of making him surprisingly popular with many players in the community, to the point he trended on Twitter, and many even mourned him when he was finally brought down hours later
. - Senji Muramasa, despite his minor appearance as an NPC story Servant in Epic of Remnant's third chapter. Being a pseudo-Servant with Emiya Shirou and having a new EMIYA remix playing during his climatic appearance against Amakusa Shirou only heightened his popularity. Since his appearance, he's been one of the most requested characters to be added every year by the fandom. He was finally Promoted to Playable as the 2021 New Year Servant.
- Tomoe Gozen also exploded in popularity after her debut in Shimosa, based on her beautiful design and being a Gamer Chick for some reason. This is despite the fact that her first mention in Babylonia was an off-screen cameo (where she was quickly killed off), and her debut in Shimosa was just as an Arc Villain who had little impact after her designated story chapter. Eventually, this resulted in her being the main Servant companion of the Setsubun event.
- Lavinia became incredibly popular despite being only a NPC in Salem because of her Creepy Cute design which wouldn't be out of place in a Tim Burton movie and her adorable friendship with Abigail. Likewise Carter also enjoys a fair amount of popularity despite him being a generic NPC because of the implications he brings to the Nasuverse at the end of the story chapter.
- The Avenger of the First Lostbelt, Antonio Salieri has generally gotten nothing but praise from much of the fandom, owing to a combination of his awesome design, his uniqueness as a 3* Avenger, his excellent animation in-battle and his outright tragic nature as a character.
- Likewise Patxi, the NPC who accompanies the Protagonist and Mash throughout the First Lostbelt and becomes the Sacrificial Lion of that story arc, has become a fan favorite, due to his amiable personality, his devotion for his old, sick mother, his character design and the fact that, despite the Despair Event Horizon he goes through, he still sticks with the protagonist and Mash until the very end, wanting for them to fight to save their world. A good boy through and through. It also helps that his name can be spelled like 'Patsy', both an endearing name and a character from a classic humor film.
- Okada Izou from "GUDAGUDA Strange Tales of the Imperial Holy Grail" turned out to be massively popular with fans in large part to his interesting character and cool design, despite being just 3* (and a limited one at that) with little advertising. He was announced in December 2018 to be the most grailed Servant of that year, beating out both Okita Alter (the SSR Servant headlining her and Izou's debut event) and Jeanne Alter's swimsuit version (already an insanely popular character in her own right and this version was a welfare Servant, free to everyone who played through her event), and has made multiple appearances in later events. He even becomes playable during the first GUDAGUDA event on Arcade, long before his official debut. He is also notably part of a very select group of Servants that have been given more than one Spiritron Dress to equip in-game. He also has the very exclusive status of being only one of two GUDAGUDA Servants to feature just by himself without bringing the entire group along in non-GUDAGUDA stories.
- Storywise, Olga Marie Animusphere is pretty much the Forgotten Fallen Friend. She died in the Prologue, and then was quickly forgotten in favor of everything else. Thanks to her quintessential Tsundere attitude during the time she was alive and then being Spared by the Adaptation in Learning with Manga! FGO, she actually garnered a substantial following even in the main story. It was not that seldom to hear the fandom using her as a rallying Battle Cry to beat the crap out of Lev/Flauros during both Septem and Solomon singularities solely to avenge her. She also appeared in Lord El-Melloi II Case Files as a Guest-Star Party Member because of that. And since she's appeared as the vessel of the Final Boss, something seems to have been planned all along for her.
- Out of the seven released bronze Servants for the game's fourth anniversary, Chen Gong received far more attention for his Noble Phantasm essentially being a reverse version of Arash's - it must kill another party member in order to be used. Fans immediately attempted to exploit it as much as they could to see how far they could go with this one gimmick. The others, notably Jason (who changed from a Hate Sink to a Butt-Monkey in just one day) and Charlotte Corday had taken lots of attention as well thanks to their earlier appearances as NPCs like Chen Gong, although in Corday's case she'd got an Early-Bird Cameo in the Lostbelt opening.
- Siduri, Gilgamesh's assistant, both in the Babylonia singularity as well as the original myth, was decently-liked for being a much more kind and polite Foil to her liege and doing her best to be helpful, but her tragic fate of being kidnapped by the Lahmu, turned into one, and despite that, maintaining her sense of self and performing a Heroic Sacrifice to save Kingu (whom she mistook for Enkidu) earned her an instant spot in many fans' (now-broken) hearts as one of the biggest woobies in the game. When Battle in New York 2019 took place, not only did she get her own Craft Essence, but she even got to replace Queen of Sheba as the shopkeeper, and she was fully voiced! Fans got so excited over this that her name (in Japanese) trended worldwide on Twitter!
- While all summer servants are meant to be popular on principle, Mysterious Alter Ego Λ AKA Lambdaryllis in particular stands out as a regular 4* summer Servant who’s popularity overrides the 5* and welfare of summer event she debuted in thanks to her First Ascension giving her an all-concealing penguin parka which helps her stand out compared to the multitude of swimsuits she's surrounded by. Her design was so loved that just about every appearance of Meltryllis in stories afterwords have her default to her summer attire while most other summer forms are lucky to get one or two story cameos.
- If the vote before the 4-star giveaway at November 2019 is any indication, Ashwatthama has a surprisingly explosive popularity despite having only been released for about half a year. Many look upon his faithfulness to the mythology, the Jerk with a Heart of Gold personality with Undying Loyalty towards his master and companions, peaking with him lending his lifeforce to Karna in order to defeat Arjuna Alter.
- Brynhild, when she debuted, seemed like a peculiar yet extremely beloved Servant. She doesn't appear in any main stories at all as opposed to her Fate/Prototype Fragments non-Saber compatriots Arash, Ozymandias, Hassan of Serenity (They appeared in the Camelot Singularity), Paracelsus and Jekyll & Hyde (They appeared in the London Singularity), and her role was basically limited to bit roles, with one gaining unexpected popularity, but overall, she just played second fiddle to the other Ensemble Dark Horse, Jeanne Alter. And furthermore, she became one of the most elusive Limited Servants after her debut, not appearing in any other banners for one whole year until she returned in the second NeroFest, but she still remained as elusive as ever. She ends up being one of the most beloved Lancer Servants thanks to her really above average capabilities as a Servant, her beautiful design by Shirow Miwa, her unique personality, her tragic litany of life and fans latched onto her so much that eventually her big break came during the second Lostbelt where she gets heavily featured (although less advertised than Napoleon) and gets her one wish to reunite with her lover Sigurd. And after that, a Summer version of hers in the fifth Summer event, and it's more likely that her elusive popularity (she rarely makes outside publication exclusive to her) greenlit Fate:Lost Einherjar, starring her daughter Aslaug, and her eventual son in law Ragnar Lodbrok. In the end, Bryn eventually got more materials compared to her Prototype Fragments compatriots despite her elusive start.
- The Servantverse counterpart of Tohsaka Tokiomi from "Saber Wars II" has proven to be quite popular for an NPC who only appears in recordings and flashbacks, being a genuinely nice and pretty badass Adventurer Archaeologist in contrast to his oft-disliked original Smug Snake self from Fate/Zero.
- Of all the Servants revealed in Atlantis, Mandricardo has stolen the hearts of players more than even the higher-rarity Servants thanks to his downtrodden but sweet personality, strong skillset, and nature as The Woobie who just wants to grasp Durandal and prove himself worthy despite his obscurity. In fact, he became the single most popular Servant to give a Valentine to◊ in 2020 just a few months after his release, beating out all the other Servants by a landslidenote
- When it comes to fanservice appeal, Yang Guifei quickly exploded in popular by her sheer design alone the moment she was released in 2020 New Year, despite lacking an actual appearance in canon before "Imaginary Scramble". She became a popular fanart subject for both safe and NSFW more than any other female Servant released a year before her in just a month.
- Several Gods that appeared in the 2nd part of the 5th Lostbelt gains this status; but most especially Demeter and Aphrodite, surpassing even Zeus, the Arc Villain of the Lostbelt. They only have dialogue sprites for their human forms and they're fought in their mechanical forms thus their battle sprites are limited to that. However, you wouldn't believe how much people wanted them to be summonable in their humanoid form, complete with new fighting styles and sprites. Aphrodite especially since she's also involved with the backstories of several Greek Servants, although mostly for negative effects, but people thought her meeting these Servants personally would be interesting. As a result, Aphrodite even ends up reappearing in the Akihabara Explosion event, taking guise of Nero Bride and is revealed to be her Proper Human History version and she's a lot more pleasant than her Lostbelt or even mythological self.
- Out of all the Fairy Knights, Fairy Knight Gawain/ Black Dog Barghest is arguably the least-important; neither Morgan's heir, like Fairy Knight Tristan, nor part of existing Round Table lore, like Fairy Knight Lancelot. But while her peers are still pretty popular, Fairy Knight Gawain is insanely popular, with explosions of fanart, fan support, and even her own subreddit less than a month after release. Her status as the most morally good of her peers also helped her stand out, and gameplay wise she is fun to use despite being another Buster AOE Saber.
- Xu Fu, the secret Big Bad of "Servant Summer Camp", is called an ensemble darkhorse by Nasu and Takeuchi in a Famitsu interview. Originally she wasn't even going to have a portrait, but they decided that she at least deserved to have one like Ereshkigal and got TAKOLEGS to make a design for her. Her having a design, combined with her true motives, made her into a quick fan favorite from the event. In fact, like Siduri before her, she was popular enough to become a shopkeeper for Battle of New York 2022. Not only that, she was Promoted to Playable during the 7th anniversary.
- Kiyohime was one of the first batch of Servants released with the game's launch and only appears in the main story every few years as a minor supporting character in each appearance. Despite that, the Japanese fanbase absolutely adores her to the point where she was added to the first Halloween event due entirely to her popularity. They're enamored by her cute design, her devotion to the protagonist, and her desire to be a good wife, Yandere tendencies notwithstanding. She regularly features in advertising in Japan, she was one of the first Servants to get a swimsuit version, and as of the seventh anniversary, she is the 3-star Servant who has been grailed to level 120 the most on the Japanese server.
- Camazotz was an instant hit with the fanbase when Lostbelt No. 7 Part 1 was released despite being a minor antagonist. He's beloved for being having a ostentatious design that's nonetheless faithful to Mayincatec imagery compared to the other NPCs who have more mundane and subdued designs, especially the gods Tezcatlipoca and Kukulkan who have taken to modern fashion, along with a deranged personality and hammy expressions to match them. His popularity grew even further when it came to light that he was able to make Alters out of Servants, all of whom have also been positively received. After Part 1, fans hoped that he'll play a bigger role in Part 2 and he'll be released as a playable Servant since the one time he's fought, we fight the generic Huge Ghost he summons. And he did indeed play a bigger role in Part 2 by revealing that he played a huge role in the Lostbelt's backstory that earned the undying respect of the fanbase, and being a Beast of Humanity with a fully unique non-ghost sprite.
- Of the four playable Servants released for Lostbelt No. 7, Tlaloc stands heads and shoulders above the rest in popularity despite being a secondary antagonist. She already garnered more interest in Part 1 than Tezcatlipoca and Kukulkan because of her cute design while absolutely rocking modern clothes in her Second Ascension, but Part 2 sealed the deal, with her pulling an awesome Last Stand against ORT and forcing it to actually go around her, the sheer ridiculousness of having a city as a Servant for the first time plus all the innuendos that come with it, and her earnest affection for the protagonist as a playable Servant winning over the fanbase. In the 2023 Valentine event just a couple of weeks after she was released, she ended in 4th place for the Servant with the most Super Lock-On Chocolates received, beaten only by long time juggernauts Oberon, Morgan, and Arcueid.
