Shuusuke Fuji has had several awesome matches, but the ones with Kuranosuke Shiraishi and Masaharu Niou are by far the one where he gets the biggest CMOA. The first one is Fuji's first loss in an official match despite him, usually a gentle Stepford Smiler, giving his soul and then some more; the second is his come-uppance and sort-of revenge on himself, which makes Ryuzaki-sensei openly say "You have finally surpassed Tezuka".
The first match where Fuji really showcases his incredible prowess is against Jirou of Hyotei, where he absolutely curbstomps him6-1 by unveiling his third counter, Hakugei. This is a result that shocks just about everyone, except for Tezuka perhaps. Yuuta, who was told earlier by Ryoma to aim for people even stronger than Shuusuke, tells him back that he'd rather keep his older brother as his ultimate goal. Ryoma ends up agreeing that's not a bad idea.
It's worth noting that Ryoma himself, though he tried to act nonchalant about it, took the first opportunity to take the coach's bench in order to watch Fuji's game up close.
The whole series is basically a CMoA for Ryoma. Understandable to some degree, since he's both the main chara and The Wesley.
His match with Jin Akutsu, which he started by shooting a ball on Akutsu's face saying "That shot was for hitting Kachirou with rocks! And why are you just standing there? There's still Kawamura-sempai to avenge. aaah, and while at it, there's Arai-sempai too". Later, when they were fighting it out at whole strangth dueing the match point, Ryoma started to loudly call the then - Jerkassout for all the puppy kicking he engaged in:
Ryoma: Oh, yeah. I still owe you something. This is for Kawamura-sempai who got juice dumped on his head! For Arai-sempai, who got beaten to bits and pieces! (...) And this is for me! Because I got hit with rocks too!
Another one comes only in the anime, more exactly in the Senbatsu: He unmasks An and lets Kamio call her out for what she did to Kirihara, and then how he confronts Kirihara and turn the tables on him.
Eiji Kikumaru's one and only singles match against Yuujirou Kai of Higa? Awesome, since this is the living proof that the usually cheery and child-like Eiji *is* an extremely skillful and strong person thanks to Character Development *and* sheer willpower-geared training. Not to mention, he never forgets the one who inspired him to develop: as soon as he wins, the first person Eiji goes to is his doubles partner Oishi. Awwwww.
Sadaharu Inui also gets one of these in his very intense, very emotional match with his "other half", Yanagi Renji of Rikkaidai.
Local Badass Normal Takashi Kawamura's CMOA? "If my power is taken away from me, then... I WON'T HAVE ANYTHING ELSE!"
His match with Kabaji alone can and will instantly turn anyone into a Taka fan.
Where do we start with Tezuka, hmm? When he defeated Ryoma in an unofficial match to tell him he should become the Pillar of Seigaku? When he beated Inui during the regulars matches? When he went against Atobe fully knowing his arm wouldn't resist the effort, yet he played SO well that even Atobe was all "...wow" in the end? When he rescued Miyuki-chan from bullies?...
It would probably be accurate to say that Tezuka is a walking CMOA machine.
A CMOA is needed for Tezuka again, for causing the extinction of the dinosaurs.
Also, An Tachibana gets her own CMOA when she turns the tables on Momoshiro during their unofficial match.
An, in the anime, is the only girl who dares to take a swing at Kirihara. She missed, but she did make him fall down a flight of stairs.
Actually, this is an Averted Trope. An's actions are clearly not intended to be seen seen as awesome, as Kamio is wrongfully blamed for the incident (which almost gets him kicked out of the camp) and Kirihara is under heavy pressure to tell the truth but refuses to do so. When Ryoma finds one of An's hairpins in the stairs, realises what happened and confronts An in private, Kamio is actually hurt and upset and calls her out on it, as he's just as pissed off as An is but he would not raise his hand at Kirihara himself.
Even cute boy Kachirou has a BIG one in the anime. When Arai badmouths Tezuka, little Kachirou lectured him and challenged the guy to a match. Maybe doesn't look like a huge thing, but when you consider Kachirou is just a sweet-faced newbie and he's facing off a second-year who's hinted to become a regular very soon... It makes lotsa more sense and makes the kid awesome.
Kaneda, being basically an extra, stepped up to his doubles partner, captain Akazawa (who by this point was putting their game in jeopardy to have a personal duel against Eiji) and called him out in the middle of the game. Althought Akazawa got upset at first, he later on thanked him for giving him that.
Kaneda: Excuse me about what I'm going to say. Idiot! Dumbass! They're playing doubles! This is not singles, Bakazawa note "Baka"="Dumb"!!