Crowning Moment of Awesome: The E3 2011 trailer as a whole. Most notably, Ezio (at 52) fighting against countless enemies unarmed. And winning. He only loses because he gets distracted by a vision of Altaïr.
The latest trailer picks up where the first one left off with Leandros about to hang Ezio by pushing him off the top of Masyaf Castle. Ezio escapes by getting the rope around Leandros, then leaping off the edge he was about to be hanged off anyway while holding the rope (with enough slack to prevent a broken neck), which causes Leandros to facefault into the wooden plank while Ezio loosens the noose (still holding onto the rope and maintaining the slack with one hand mind you) and drags it over his head. Ezio then falls several stories straight down, lands on his feet and not only DOESN'T break his legs, he then gets up and walks away while unconcernedly flipping his hood back up. Bad. ASS.
Better yet? It's canon, as the first memory of Sequence 1 starts immediately from Ezio's walking away.
What makes this scene better is that before he's about to be hanged, he's led through a room with about twenty or so people in it, armed to the teeth. His wrists are bound together, completely unarmed and is being dragged to his death. After a few moments, he simply gets up and begins to walk on his own, and everyone in the room freaks the hell out.
Not to mention that the whole sequence is so amazingly detailed that it looks seriously lifelike. A few times one could confuse it with real people for a moment if they didn't know they were looking at a video game trailer. Truly amazing.
Ezio manages to sink an entire Ottoman fleet by himself, with a Greek Fire cannon. Complete with a, "cool guys don't look at explosions" finale.
And before that, Ezio plants a bomb directly at the base of the Great Chain, walks away a bit and shoots it with his Hidden Gun. It explodes... not only dislodging the Great Chain, but bringing the entire building down! Yusuf was not kidding when he said it had fifty times the kick of their usual bombs.
Ezio scaring off Duccio. The moment itself counts as a Crowning Moment of Funny, but the awesome part is Duccio's reaction when he sees Ezio.
Duccio: "THE DEVIL HIMSELF!"
Altaïr showing what he learned from the Apple of Eden while he was in exile.
Altaïr: That is true, Abbas. I have learned many things from the Apple. Of life and death, of the past and the future. Let me show you...
Tutorial: Use the gun to kill Abbas.
That entire sequence is a Crowning Momentof Awesome... starting from when a very old Altaïr walks into Masyaf and almost immediately the loyal Assassins begin to follow him and you can see them running back and forth taking down the corrupted Assassins as Altaïr quietly walks through the village.
As you make your way into the fortress, a few remaining dissenters will come and attack Altaïr. You have the option of killing them (though you will lose Full Synchronization) or knocking them out, but if you choose to disarm them instead, they suddenly back off and decide it's better to pledge their allegiance to the returning mentor rather than facing utter defeat.
On top of that, after what he did to Altaïr's loved ones and the decay brought upon the Brotherhood during his reign as Grand Master, it felt immensely satisfying to finally kill Abbas.
Desmond Sequence Five in general, as you end up back at Abstergo, retracing your escape route from Assassin's Creed II all the way back up to the Animus room — where it all started.
When Ezio arrives at Sofia's shop all that's to be found is Yusuf's body and a shitload of dead templars. Proving his status as a Badass.
There's a total of fifteen Templar corpses in there, which means that he alone killed them, as well as probably wounding several others.
When Ezio leads a Roaring Rampage of Revenge against the Templars for killing Yusuf and kidnapping Sofia. He basically leads an army of Assassins straight into the heart of the Templar headquarters. The fact that you have an inexhaustible Arrow Storm bar and a whole squad of Assassins as personal bodyguards means that Ezio can get through the level without ever physically touching an enemy himself.
Altaïr escorting Niccolò and Maffeo Polo out of Masyaf. He can't even run past a light jog anymore, but he still definitely qualifies as a Old Master because he makes up for his decreased physical ability with control over the Apple of Eden greater than any we've seen before. He creates golden Assassins that fall on enemies from the heavens, his range is big enough to cover a significant portion of the village, and best of all, it's not Cast From Hitpoints.
Ezio beating the crap out of Prince Ahmet, while both of them are falling off a cliff above a cemetery. And it was in slow motion. And instead of letting Ahmet fall to his death,he saves him so Ahmet can get killed by the right person. And the whole scene leading up to that was just...awesome.
To elaborate on the preceding scene: Ezio is paragliding behind the cart Sofia is driving, and is swooping down to assassinate horse riding enemies, either by hidden blade or by throwing them at the other riders.
Shahkulu, while being a relatively minor villain in the story, certainly qualifies. Unlike other antagonists who either run away cowardly or die trying to explain their motives and whatnot, Shahkulu quite literally LAUGHS at death's face. Even Ezio himself seemed surprised.
That's not all. The above happens right after Ezio leapt off a vantage point to perform an air assassination on Shakhulu. Then, as Ezio walks over to his body to confirm that he's dead, Shakhulu starts choking Ezio, giving an Evil Laugh. He pulled a No-Sell on an attack that killed every single person it has been used on in one hit.
And when Ezio stabs him a second time, he slowly chokes after a few seconds, making it seem like he's finally dying... but he gets up anyway, and Ezio has to personally fight to kill him.
In Sixteen's final cutscene with Desmond, both Clay's dialogue and his actions are Crowning Moments of Awesome. When the Animus starts deleting Animus Island, and attempting to delete Desmond's mind, Clay sacrifices himself so that Desmond can escape into Ezio's partition, buying him enough time to find a Synch Nexus. It's also the moment when the player finally knows, once and for all, whose side Clay is really on.
Sixteen: What is a man but the sum of his memories? We are the stories we live! The tales we tell ourselves!
Desmond: [desperate] Don't do this!
Sixteen:I'm saving you, idiot! [shoves him toward the gate] GO! GO!
At the end of the very first sequence, after Ezio climbs to the top of Masyaf's castle, he performs what is probably the most badass and daring Leap of Faith in the series. He takes a short moment to look at the ground, pushes a statue from the top of the castle, and before the statue can even make contact with the ground below, immediately performs a Leap of Faith right after pushing the statue. Said statue creates a hole through the ground and exposes the pool of water beneath that breaks Ezio's fall just before he is able to make contact with the ground. Ezio performed a literal Leap of Faith!
Assassin's Creed: Embers
Shao Jun and Ezio get a few awesome moments when fighting the Emperor's agents in Embers, but the crowner has to be when Jun slits a bad guy's throat with a hidden blade in her shoe. Using a roundhouse kick.
The Emperor's agents attack Ezio's villa at night. Ezio gets more kills than Shao Jun, who is probably a third his age and in her prime. Not to mention he pulls off a hook-and-run, without the hookblade, a disarm counter, and nabs another kill by throwing his poker through a dude's eye. Not to mention his flying, spinning stab that gets another guy in the eye. Along with that, he jumps out a window and kills the truck of a man while being tackled. And at the end, the old Mentore laughs it off, as if saying 'Still got it.'
The unnamed Brute agent gets one: he got stabbed through the goddamned eye by Ezio, and is clearly obvious pain, but it didn't slow him down at all.