Rosario + Vampire/Awesome

In episode 9 of the anime, after Ruby critically wounds Tsukune, Moka is so distraught that this overcomes the rosary seal and unleashes Inner Moka, who stands up glowing with power as the rosary shakes with the effort of trying to restrain her. Next, Mizore and Kurumu's eyes start glowing as they power up in anger, Mizore freezing the area around her and Kurumu transforming and saying "How dare you?" Ruby's expression as Kurumu flies at her says it all -- just before the episode ends with an explosion of power into the sky.
- Heck, the entirety of episodes 9 and 10 (the Witch Hill arc) is easily one of the best parts of the anime. Sure, they changed some things around, but then we wouldn't have gotten the scene where Tsukune is running towards the house and skids to a stop as yet another plant monster pops up in front of him, only for it to get shot to pieces by Mizore, who we see is standing further back along the path. All hail the long-range fighters!

Manga: Season I

Ginei Morioka gets one of these when he defends the rest of the newspaper club from the yoko Kuyo. "A new school rule just got passed. Anyone who raises a hand against any member of my club...gets ripped to shreds!" Maybe he's just a Jerk with a Heart of Gold, after all?
In the manga, Tsukune's ghoul form fully awakens and stops a hybrid monster that almost kills him and "Inner" Moka with one punch. Too bad that With Great Power Comes Great Insanity and he goes nuts afterwards
Following the line of the first example, Gin arguable kicked off the whole line of CMOA's when he blocked a mini-arc's Big Bad's strongest attack. This falls in because he had enough absurd speed to dodge it, but took the attack anyway to prevent everyone else from being barbeque'd. Tsukune quickly upstages him, though.
To be fair, any time one of the good guys starts kicking ass, you can practically hear 'Number One' from Bleach kicking in, only without the inevitable record-scratch, and tragic pounding of the would-be hero. It's actually quite refreshing.
- That's not to say it doesn't happen, though. Take Hokuto for example. His first fight is a "loss" against 4 (count em', 4) of the True Companions. But when he fights Tsukune alone, it's a Curb Stomp Battle. Tsukune feels Moka's desperation elsewhere (presumably through a blood-related connection they share) and gets back up. Then... Hokuto mercilessly continues to beat him.
Every single time tsukune goes into his 'battle mode' or 'zanryu ketsueki' as inner moka calls it, which Tsukune normally transforms into when he is injected blood. As long as he doesn't transform into a ghoul, his speed and strength go off the charts while taking the identity of a silent, badass protector. In fact he only speaks in this form once when the earthworm youkai gets obliterated by Tsukune when it tried to kill Mizore and Kurumu, he says "Unforgivable, you even hurt my friends, I won't let you off". This dialogue is reminiscent of ss2 gohan from the cell saga.

Season II

Kurumu gets her Crowning Moment of Awesome during an amazing Tear Jerker Crowning Moment of Heartwarming scene. Mizori attempts suicide by jumping out of a window after a near-rape by an unwanted arranged fiance. Kurumu immediately leaps after her and catches her before she impales herself on ice shards on the ground. With Mizori crying about being ruined forever -- he did everything but physically rape her -- Kurumu does the one thing that will tell Mizori that she is not "ruined forever" as a lover - she plants a long kiss on her, breaking it apart and tearfully saying "A kiss isn't so bad, is it?" Mizori hysterically cries, "He touched me everywhere. I didn't have time to resist. I was so scared!" -- and finally breaking down and crying like a baby in Kurumu's arms, who cries along with her, holds her and tells Mizori "It's all ok now."
In the flashback arc of the manga, Moka's mother, Akasha Bloodriver has one as she gets up after being cut in half by Akuha, healed already, saying it's not enough to kill her thanks to her Healing Factor as a Shinso. She then proceeds to strip off her robe to reveal her battle underwear and literally pulverize ~~the alien queen~~ Alucard who is also a Shinso, with kicks so powerful that it can't regenerate, while she drops the famous catchphrase of her daughter.It then also becomes a Crowning Moment of Heartwarming as she lets herself get stabbed only to save Moka in time.
Gin pulling off a Xanatos Gambit to get into a "Fairy Tale" base and then beating seven kinds of crap out of the member he tricked. Then deciding to take out the entire organization when he finds out they threatened Sun, who he considers the most important person in the world to him.
- Don't forget Haiji. Yes, Haiji. The Karate Captain who you thought was a throwaway joke character? He shows up when Gin calls. He also happens to know Sun-sempai. He's also quite irritated that people have threatened her. By the time he shows up, the duo don't even have to try to take apart the enemies and they're growing quite bored of the whole thing. And the kicker? Sun was the strongest ayashi of her generation, which she quite handily demonstrates to the regional leader of Fairy Tale.
Tsukune gets one during his rescue of Sun and Moka. His confidence is destroyed because Inner Moka tells him how much he sucks at fighting and that he'll just get in the way. Later on, while easily dodging knife stabs and bullets, Tsukune realizes that he only sucks compared to Inner Moka. And basically everybody sucks compared to Inner Moka.
- It wasn't so much that he was a bad fighter, it was just that he lacked confidence and aggression, which he quickly got over when Moka was in danger. In fact, physically speaking, Tsukune is probably stronger than Moka, and is not affected by normal vampire weaknesses.
  - The weakness part is probably correct but since, as explained in some chapters vampires doesn't use muscle they instead turn their yokai power into pure strenght and so Tsukune probably isn't stronger since he isn't born a vampire and only turned into one. But future chapters will probably look at this more.
  - Right...except that the only time when Moka fought a fully-powered Tsukune, she had to do so with every ounce of her strength and with absolute killing intent. She knew full well that if she went anything less than all out, he would kill her. And even then, that was when he had roughly zero actual combat training, and was caught completely off guard and off balance by Moka's assault.
  - Yes, but remember that shortly before, Moka was severely weakened by all of the water from the sprinklers. That means that she wasn't fighting at full strength.
- Him fighting Kanade afterwards also deserves a crowner. After his Death Melody blinds him, he puts to test what Inner Moka taught him about monster energy (yoki) and beats the crap out of the mermen he summons. Then he charges at Kanade, who had taken Sun out of the fight underhandedly, but she manages to recover and envelop Tsukune with a barrier so he can punch the LIVING FUCKING DAYLIGHTS out of the chicken-legged bastard.
  - Not to mention Sun's been giving him the coup de grace all along by singing an inaudible ultrasonic tune, designed to break Kanade's body apart from inside. Really, its gratifying to see such an asshole plead for mercy in his final moments and, befittingly, being conceded none.
    - San's speech prior to delivering her Silence in the Dark technique deserves a mention.

San Otonashi: "I've been singing since this battle began. An attack melody sung in a pitch so high you can't hear it. As high-pitched as the ultrasonic call of a dolphin. The song you couldn't hear has been disintegrating you from the inside out, and now your own body can't endure you singing such a powerful song! You're falling apart as we speak. You'll never be able to sing. Prepare yourself, Kanade Kamiya. You killed Ms. Marin's beloved husband. You deprived her of the future she dreamed of. You've hurt my fellow students. [This next bit is written on her notepad] For all of that... you are going to pay. (Kanade tries to attack) I told you. Your body is gradually disintergrating. [Back to speaking] And since Tsukune's attack, it's about to fall apart. An inaudible song. Invisible destruction. That is my power... Silence in the Dark."

After Mizore gets kidnapped, Ruby, Moka, and Kokoa just walk right into the building, then pull out an insane number of guns and start shooting. Better yet, this is just a distraction so Tsukune, Kurumu, and Yukari can get in undetected.
Ling Ling gets two, one right after the other during what appears, at the time, to be a Heroic Sacrifice. She starts by fighting Akuha to a standstill, with the latter bluntly informing her that she's going to get tired first. Ling Ling responds by whipping out an uzi and emptying it into Akuha point blank. When that doesn't work, she lets herself be cut in three to ensure she can trap Akuha in a magic circle which heats everything within to thousands of degrees. Bad. Ass.
Chapter 41: Kurumu breaking through a barrier that should have killed her and bringing Tsukune back to sanity solely through the Power of Love
You don't get much more badass than this. All hail Tsukune!
Chapter 45 of the second season of the manga features Ruby saying the following while getting up after getting beaten by Raika: "I'll fight. There's no way I'll let him lay another hand on anyone!"
Chapter 46: Outer Moka putting her faith in her friends and vowing to hold Alucard back until they can reach her. And Ruby using her Iron Maiden magic and taking the strongest attack of her opponent to get him in a position where can hit him with her strongest attack ending the fight. She even pulls off a cool pose despite all the damage she took.
Chapter 47 of part 2: When Fong Fong saves Yukari from Routier. "I don't care if you hurt me. But don't you dare lay your hands on my friends."
- He one-ups it next chapter, finally realizing his talent doesn't lie in summonings, but Martial Arts. Yukari, on the other hand, became adept at summoning enough to impress the enemy. Making them the Sword and Sorcerer duo.
Chapter 52. Because a) Tsukune kicking ass, b) the Calvary and c) motherfucking dragons.