And prior to this, if you've leveled up the Main Character enough, you can get his ultimate persona, the Messiah. Yes, the Messiah. He can be created to use instant-kill light and dark magic, comes with one of the most powerful physical attacks (Hand of God, no less), plenty of resistances, and can learn the full-party perfect healing spell and - in tasty irony - become immune to piercing attacks. Holy shit.
"We're going to summon that guy to do battle with the incarnation of death itself. This game could not possibly get any more metal."
Junpei Iori and his epic jump from fail to awesome. After Chidori, a member of Strega, tries to kill him, he's still believing in her until the very end, promising to protect her until the end. Then Takaya shoots him once, killing him instantly - at which point Chidori sacrifices herself to bring him back (in itself a CMOA for Chidori). After her death Junpei makes his ultimate revelation, upgrades his Persona and proceeds to blow Jin up.
Did we forget to mention that Jin(the guy who Junpei blew back) 'absorbs' fire(Junpei's respective elemental affinity)?
If it could blow back a guy who absorbs fire, what would it have done to Takaya, his intentional target?
Actually, Jin repels fire, so more accurately Junpei's attack should've hit Jin and bounced back and hit him in the face(doing nothing because Junpei's Resolved Persona is immune to fire). Junpei is so awesome in that scene HE BREAKS THE GAME MECHANICS when Jin takes the hit for Takaya. Gotta wonder how surprised Jin was to get laid out by that attack, because he had to know what his Persona resisted.
Shinjiro Aragaki is nothing but CMOA. Sacrificing yourself to save the kid who has been planning to kill you for two years can't not be epic, surely.
Gameplay evidence of how awesome Shinjiro is: his critical hit animation involves a headbutt. This is true regardless of the opponent, meaning that it's possible to see Shinji fearlessly headbutt a Shadow tank. Bad Ass.
Not to mention that he could still walk after he was shot twice by the most powerful production handgun in the world
For me, the crowning dramatic moment in the game is the moment Aigis shouts "Palladion!" and Unavoidable Battle starts playing as her showdown with Ryoji truly begins. Everything about that cut scene is just brilliant, crowning perfection. The way his voice changes from a frightened, confused kid into grim understanding and confidence, the way the animation flashes back and forth between the past and present battle to show how history's repeating itself, and Aigis's tone of voice, both emotionless and pure 200-proof determinator at the same time, for the following line...
"A machine is created for a purpose. Mine is to defeat you."
To elaborate on this, the last time that she fought him, he was only one-thirteenth as powerful and still Aigis was unable to defeat him, instead having to seal him away. This time, he's at full power, meaning Aigis has no chance of even making a dent in him...and she attacks anyway because it's her mission.
Even Fuuka gets one when she first awakens her persona.
Koromaru gets one when he stops Ikutsuki from using Aigis to kill the members of SEES on top of the observatory Especially awesome when you realize he had to run straight through the building to get to Ikutsuki. Someone get that dog some steak.
Even better, in P 3 P, if you play the girl, not only does Mitsuru's father tell Ikutsuki to shut the hell up on his Motive Rant, when Ikutsuki pulls out a gun and shoots him, he pulls out his own and shoots him right back. That's one Dying Moment of Awesome.
During the later ranks of Mitsuru's social link she tells him/her how important the main character is to her, only to be confronted by her jerkass fiance. He proceeds to berate the main character with insults and telling Mitsuru that she's only to be his obedient wife. Mitsuru decides she's had enough of that crap and delivers a delightfully awesome speech to her fiance and causes him to run away in terror. (In Portable, this happens whether you play as the male character or the female character.)
In the penultimate rank of the Hermit Social Link in the female protagonist's route, the PC gets fed up with the way everyone is treating Saori and encourages her to clear things up - by hijacking the school's PA to share her thoughts with the whole school. While Saori is making her announcement, the PC guards the door and refuses to let Mr. Ekoda to get in to stop the broadcast. Then Ms. Toriumi and Ms. Ounishi show up and proceed to completely stonewall Ekoda, clearly enjoying every minute of it. After sending him on his way, they cheerfully admit that they see nothing wrong with the stunt and have no intentions of punishing the girls for it. It's a small thing compared to facing down an Eldritch Abomination, but damn if it's not incredibly satisfying all the way around.
This isn't quite on the same scale as the others, but when Fuuka disappears, Mitsuru discovers that Mr. Ekoda knew something had happened to her and covered it up. Mitsuru gives him holy hell about this:
Mitsuru: For the sake of your job, you ignored your responsibility as a teacher!