Anna taking down a wolf with a lute. When more wolves grab Kristoff, she lights a sleeping bag on fire and throws it at them.
Shortly after, Sven making a large leap across a gorge.
How about Kristoff putting Anna on Sven's back and cutting the harness when he sees the ravine, making sure that even if he doesn't make it, his best friend and the young woman in his care will? That's a crowning moment, an Establishing Character Moment and an Heroic Sacrifice all in one, folks.
"Let It Go." Not only does Idina Menzel's performance knock it out of the park, but the song is also a breakthrough for Elsa, finally happy after spending so much of her life scared and restrained.
The stunning sequence where she raises her ice palace. Not only is it a gorgeous bit of animation, we have a full demonstration of Elsa's true power.
The "Let It Go" sequence was amazing in general, but special mention goes to the moment where she magically creates her Snow Queen outfit.
Anna rescuing Kristoff from falling over the cliff by throwing him the pickaxe and rope.
Anna yelling at Marshmallow after he throws Olaf.
Hans and his men fighting against Marshmallow.
And right after that, Elsa taking on the Duke of Weselton's lackeys with her ice powers.
The Reveal of Hans as the Big Bad and a Sociopath is this (while doubling as Nightmare Fuel), since he managed to fake being nice so well that without a spoiler of some kind or picking up on clues from his character design, there was no way anyone watching would see it coming!
Also notable is how this subverts the Broken Aesop it looked like we were going to get for a while about Anna and Kristoff's love being the key.
After summer is restored to Arendelle (which is a CMOA for Elsa by itself) and the main characters are on a ship in the fjord, they see Hans getting up and Anna gives him his desserts for almost killing Elsa.
Hans: Anna? But she froze your heart!
Anna: The only frozen heart around here is yours. (turns away and decks him, knocking him into the fjord)
Followed shortly by the royal guests applauding Anna. And most likely the audience too.
Sven and Kristoff galloping across the frozen fjord in a huge ice storm to save Anna, as the frozen ships begin to collapse around them.
Kristoff marching his way to go throttle Hans for what he almost did to Anna. Luckily, (however you look at), Anna stops him. What makes this moment awesome, is that it shows that you NEVER want to mess with the people Kristoff loves.