Here are some of my favorite scenes from My Little Pony Friendship is Magic:
From Sonic Rainboom, any scene showing Rarity with her butterfly wings, and when Fluttershy jumps up and down (almost like Pinkie Pie) when Rainbow Dash actually does the sonic rainboom (event).
From Three's A Crowd, when Discord is revealed near the end of the episode to have been faking his infection with the blue flu. He is confronted by Twilight Sparkle and Princess Cadance, and the draconequus tries to explain his chicanery as a test of Twilight's friendship. Then the Tetzulwurm throws up on Discord, who turns green and actually becomes sick.
From Hearts and Hooves Day, when the Cutie Mark Crusaders use a love potion to make Cheerilee and Big McIntosh fall in love with each other. Also at the end of the episode, when Apple Bloom, Sweetie Belle, and Scootaloo are doing BIg Mac's chores at Sweet Apple Acres as punishment for the love potion, Cheerilee and Big Mac fake still being under the potion's effects and the CMCs scream, "NOOOOO!!!"
In Dragonshy, when Fluttershy uses The Stare on the adult dragon.