Awesome / It's a Dangerous Business, Going Out Your Door
Applejack saving Rainbow Dash and Rarity from the cave on the mountain by bucking the wall hard enough to make the cave collapse.
Applejack standing up to Lord Hammer Hoof and telling him he was wrong in his own court and in front of all his people. And she was right.
The three of them teaching the Gildedale ponies how to herd the komagas, saving them from ever having to fight them again.
Rainbow Dash learning to summon and control lightning better than any other Pegasus except Firefly.
Rarity gets one for talking down Lady Falalauria, who was considering killing her and her friends to prevent a disaster that might come to pass in the future.
Rarity being completely calm as she is flung miles into the sky by the World Snake, actually managing to take out the bottle of fire, open it, and send the flower off in it. And then as she plummets to her death, she still remains calm.
Applejack standing firm earlier in the battle in chapter 18.
Allow me to expand: Applejack standing not only firm, but firmer perhaps than any Earth Pony ever had before and basically turning herself into an extension of the earth. When the World Snake crashed into her, the impact fractures the ground around her for miles and levels nearby mountains.
And remember, this is the equivalent of someone being hit in the face with Guam.
Don't forget Rainbow Dash, who basically became a one-pony army as she attacked the World Snake by shooting it with lightning in its enormous face.
Screw it, the whole World Snake battle is one long CMOA.
Rarity's epicRousing Speech at the beginning of Chapter 18, convincing her friends that now is not the time for retreat because Twilight needs them.
And of course, we can't forget Twilight, who teleports across two countries to save them from being killed by the World Snake, having nothing to go by but a vision brought on by horn rot. And this is after stating clearly that she doesn't believe in visions. It also turns out that she teleported through a strong magical barrier created by the World Snake. Twice.