Mega Man Classic
- Many Robot Masters from the NES era still have a solid fan base, including but not limited to: Metal Man (due to his design and overblown weapon), Shadow Man (design and difficulty), Skull Man and Pharaoh Man (both looking badass), and Sheep Man, originally The Scrappy when Mega Man 10 was announced, but ultimately became this when the game came out.
- And of course, there's the original Proto Man, who gets cool points for being Mega Man's brother, a rare robot that's neither allied with Light or Wily, and having a pretty great design and memorable theme, even if his actual boss fights as Breakman are pathetically easy. He's made playable in the 9, 10, and Powered Up.
- Roll, Mega Man's little sister, has a fanbase of her own, even if not to the extent of Protoman's. She's adorable, a kindhearted Nice Girl, helpful in her few prominent appearances, has a crush on Mega Man (only in Powered Up, thankfully), and received a very pleasing redesign in Mega Man 8, one of the few things to carry over into the ninth game. While she was little more than a background prop in the NES games, the seventh installment gave her some speaking lines, the eighth upgraded her to shopkeeper, Powered Up made her a playable character with a goofy and fun playstyle, and has a surprisingly sad cutscene in the tenth game. She's become a Fountain of Expies for the female sidekicks later down the series who have all become popular themselves who share some aspect of her design and personality, including Iris, Ciel, Casket, and her Exe incarnation. Becoming a Lethal Joke Character in multiple fighting games earned her some attention as well. She even got her own series of character mods in the classic games!
- Splash Woman (from Mega Man 9), who has a huge fan base and has made many players robosexual. Aside from Roll, she's one of the very few female characters in the series, let alone for the Classic timeline.
- Enker, Punk, and Ballade, or the Rockman Killers, a group of Robot Masters created for the sole purpose of offing the Blue Bomber. Making their debut in the Game Boy titles (Rockman World in Japan), they subsequently reappeared in Mega Man V for one final battle with Mega Man (alongside Quint)... and then resurfaced years later in 10 as DLC Bonus Bosses. You can also obtain their weapons.
- Also from Mega Man V, Sunstar, for his cool design and acting as the final boss in a series whose only final boss tends to be Dr. Wily.
- Tango the robot cat only plays a major role in the Game Boy Mega Man V and makes a few minor cameos elsewhere, but his adorable design and general usefulness earned him many fans.
- Bass is popular in some circles, although his largest fanbase is still his .EXE incarnation, which fans literally seek out ways to play as him or use a soul of his more than any other character despite his lack of availability, barring one game, and consider him to be the undisputed strongest character in the Battle Network games, barring certain events.
Mega Man X Series
- Zero from the Mega Man X series was originally intended to be just in the first game, hence his death; however, he turned out to be so popular that he was revived in the second game. He even got his own critically acclaimed series of games later on.
- Keiji Inafune, the producer of the Mega Man series, originally designed Zero to be the main character in Mega Man X. Believing that players wouldn't be able to accept Zero as the new Mega Man, since he was radically different from the original one, he instead redesigned Mega Man X to give him a greater resemblance to the original blue bomber and used X's original design for Zero, a supporting character. Inafune actually admits that Zero was a bit of a Canon Sue, since he gave Zero some of the more important scenes in the game (source). In other words, Inafune just invoked his status as a darkhorse.
- Later, Zero was going to be written out of the X series by having him die for good in X5 (Intended to be the end by creator Keiji Inafune) and wake up with no memory in Mega Man Zero. X6 revived him yet again, putting him in a pod for 100 years to come out in Zero. However, they wanted to use him in the X timeline again, so this scene (Zero's ending in X6) was declared to be a "bonus ending" taking place after the rest of the series.** Eventually, both Tron Bonne (mentioned further down) and Zero found their way onto the Capcom Vs. Fighting Game series. Tron and Servbot in Marvel vs. Capcom 2 and Tron returns in Marvel vs. Capcom 3 and Zero in the Updated Re-release of Tatsunoko vs. Capcom (Ultimate All-Stars) and Marvel vs. Capcom 3. Zero also appears as a secret character in SNK vs. Capcom: SVC Chaos. Both of them also appear in the Turn-Based Strategy Project X Zone.
- In terms of Maverick bosses, there's Storm Eagle and Magma Dragoon.
- Zero may have been involved with a lot of girls, but one girl stands out as the ultimate Darkhorse ladies: Iris from X4. Aside of being utterly adorable and one of the girls that Zero truly loved, her tragic death (albeit a little ruined thanks to the Narmy dub) is considered one of the most powerful moments of Zero's life and won her a lot of fans. Capcom has been compensating to make her get more screentime by featuring her in the GB game Megaman Xtreme 2, which is a prequel... and years later, puts her along with Zero in the crossover Project X Zone. She's not playable, of course, but considering that Bandai Namco, the company behind Super Robot Wars (known for preventing tragic canon deaths) is on the head development...While she did stay dead, Iris did appear for one scene, which is considered one of the most memorable moments in a game filled with beloved characters.
- From Mega Man X2, the Green Biker Dude who dies in the beginning of the first level has attained meme status.
Mega Man Zero Series
- Harpuia became a huge Ensemble Darkhorse during the run of the Mega Man Zero series because he was likable Anti-Villain that ultimately showed himself to be a Hero Antagonist and later full blown hero
- The Zero series spawned a few minor/temporary ones, like Chilldre Inarabitta and Leviathon.
- Omega. This Ax-Crazy psychopath was popular enough that he came back as a bonus boss in ZX. Of course, he's Zero, so this shouldn't come as any surprise.
Mega Man ZX Series
- Girouette was almost one for the Mega Man ZX series until it turned out he was a Sacrificial Lamb. Come to think of it, he might be one anyway.
- Another ZX example comes in the form of the villainous Brother–Sister Team known as Prometheus and Pandora. A Red Oni, Blue Oni Evil Duo consisting of a badass Ax Crazy Awesome Grim Reaper and his emotionless Dark Magical Girl of a sister, the fandom has been warming up to these two from day one. They've garnered even more of a fanbase since they've been revealed as Woobies, Destroyers of Worlds due to their horrendous childhood. The stellar music that accompanies their multiple appearances also helps. How much do the fans like them? So that much that there was an outcry when Master Albert, the Magnificent Bastard of the series, owned them. Fans are hoping that the ambiguous nature of their "death" can allow for a reappearance in the future. That, and Pandora is ADORABLE.
Mega Man Legends Series
- How about the Bonne family from Mega Man Legends? A family of comically villainous pirates who have some hilarious dialogue and help to liven up an already colorful game. Seriously, they got their own spin-off game!
- There's also Tron's Servbots. Their popularity led to one being a joke character in Marvel vs. Capcom 2: New Age of Heroes, and one of Tron's super combos is summoning all 40 Servbots (sans the one following her) to Zerg Rush her opponent.
- Eventually, both Tron Bonne and Zero found their way onto the Capcom Vs. Fighting Game series. Tron and Servbot in Marvel vs. Capcom 2 and Tron returns in Marvel vs. Capcom 3 and Zero in the Updated Re-release of Tatsunoko vs. Capcom (Ultimate All-Stars) and Marvel vs. Capcom 3. Zero also appears as a secret character in SNK vs. Capcom: SVC Chaos. Both of them also appear in the Turn-Based Strategy Project X Zone.
Mega Man Battle Network / Star Force Series
- Colonel.EXE, Protoman.EXE, Tomahawkman.EXE, Searchman.EXE, and Bass.EXE—freaking INCREDIBLY popular from the Mega Man Battle Network game/Mega Man NT Warrior anime-manga series.
- Sonia Strumm/Sky is this for western fans due to being one of the most likable and sweet characters of the cast and being actually capable of fighting semi-evenly with Mega Man. She's also, like Tron, pretty cute.
- A.C. Eos is fairly popular as well for being both very relaxed and likable, and being fairly complex as the game later shows.
- Hyde became somewhat subject to this to those who watched the Tribe season of the Mega Man Star Force anime, as he was changed from a sycophant quasi-Dragon in the game to an out-there, comic relief artist in the anime. It didn't hurt that his crowning moment of villainy was kidnapping the hero's mother and throwing her off buildings and bridges Green Goblin-style just for the lulz.