Right before the Battle of 1000 Heartless, Sora runs down a ravine fighting Heartless without Donald or the believed dead Goofy, but he isn't alone. Yuffie, Tifa, Cloud, and Leon join in one at a time.
The Gummi Ship Course "Assault of the Dreadnought", which pits your ship against a massive fleet of Nobody warships, including their flagship, the titular Dreadnought.
The mission itself revolves around you fighting your way through the Nobody fleet so that you can enter the Dreadnought and destroy the reactor core for its Wave Motion Gun. Not only will destroying the core get you some rare Gummi Blocks, you are also treated to a gorgeous view of the Dreadnought blowing up.
Auron's role in the Hercules stage is somehow even more awesome than anything he did in Final Fantasy X. He gets brought back from the dead by Hades to kill Sora, practically spits in his face in return, and goes off to team up with Sora and kick all kinds of ass.
And even after he's teamed up with Sora, it doesn't end there: When Hades makes Auron his slave by brainwashing him and forces him to battle against Hercules, he doesn't only keep his stance: He is winning, only minutes away from wiping the floor with Hercules when Sora and the party storm in and free him from Hades' control. Let me repeat that: Auron not only survives a battle against a super strong demigod, but he's kicking his ass without breaking a sweat. I don't think it can become any badass than that, ladies and gentletropers.
The final battle Sora and Riku vs. Xemnas. Special mention goes to the very end, with how Sora and Riku are able to coordinate their actions with very little words exchanged. That's the definition of Bash Brothers.
Port Royal, as a whole, is an extremely wholesome experiance. You fight the Undead pirates, blast other pirates ships, essentially get a retelling of the movie and a sort of continuation on the second visit, fight Barbossa and an Aztec Grim Reaper heartless as bosses, and actually see blood- even if its just a cut on the hand. Jack Sparrow is as cool as he was in the movie, even being able to weld a keyblade for a short time; and it is interesting to see the stylised, anime-ish, and realistic characters clash (particularly Pete conversing with Barbossa.
The scene before Barbossas boss fight, where The heros pull a Big Damn Heroes, there's a swordfight, and The Illuminator is introduced, letting Barbossa get a cool pose with it's Glowing Eyes of Doom.
Shadow Stalker's and Twighlight Thorn's back-to-back boss fights.
Timeless River, sort of celebrating the past of Mickey Mouse before Epic Mickey did.
Tron smashimg Sark in the face with his disk in Space Paranoids.
During the boss battle after this, once the MCP takes enough damage, Sark will sometimes put up a wall to stop the party from fleeing... which will allow Sora to perform a reaction command that will allow him to stab Sark in the head and instantly kill him! BIGMISTAKE, SARK!
The Storm Rider boss fight where you can hitch a ride on the bosses back.
Doubly awesome if you finish him off with the reaction command under his stomach, which causes Sora to deliver some quick strikes to his belly, send him flying into the air, and lands with a pose as the Storm Rider slams into the ground behind him and dies.
Being able to combo Past!Pete into Present!Pete to, in effect make him hit himself with a shockwave.
The Experiment, which shows how much research was put in as the creature is a mis-mash of background props from The Nightmare Before Christmas (For example its right arm is part of the scenery in Dr.Finkelstiens lab).
Ken Page redoing his voice as Oogie Boogie.
The Hostile Program, which is one of the few characters that isn't from Disney or Square Enix that isn't in the main cast, is fought as the boss on Spaces Paranoids first visit, and after which is where the game starts to heat up a little. (YMMV on opinion though)
Shang knocking Shan-Yu over and then taking the Emperor in to safety.
Actually if you're proficient enough at Guard/Reflect (not that the game ever gives a proper tutorial on them) Prison Keeper is very manageable even at level 1. Which makes the fight more awesome in that you'll be deflecting his attacks back at him!
The final Roxas vs Axel fight. Dual wielding keyblades? Check. Huge ring of fire? Check. Bashing away at Axel with these two keyblades while running sideways on the ring of fire? Double check.
Any time you summon Genie, it usually ends up being very spectacular. Especially in KH II, where he mimic's Sora's drive forms.
It might take him a little while to shake off his Heroic BSOD this time around, but once he does, The Beast is just as awesome as he was in the first game. A common complaint of this game is that the Disney worlds are mostly Filler, but Beast continues his streak of being relevant by personally helping Sora rip Xaldin apart, (with a little help from Belle's elbow).
For that matter, Belle's actions in general - rather than play the role of Distressed Damsel and force beast to make a Sadistic Choice, she just has none of it and elbows him in the stomach, grabbing the rose and running to safety.
A manga example is Sora taking out a Magnum Loader after Donald accidently grabs onto it while playing with a Light Cycle. Sure, everyone else enters a Heroic BSOD due to the required piece of data needed for the trio to escape is destroyed, but seeing Sora taking action before that is pure badass. Not to mention that he uses his Keyblade to repair the broken data.