The Sound Invasion arc was awesome enough, but the battle between Orochimaru and Sarutobi was just incredible, especially since Luna was backing the Hokage up. Awesomeness ensues. Especially since Luna is throwing meteors at Orochimaru.
Twilight Sparkle lifting the entire ninja train in Snow Country and derailing it!
Fluttershy giving Tsunade "The Stare" when they had to retrieve her to take Hiruzen's place as Hokage, while giving her one hell of a "What The Hell" speech, and it actually having an effect on her.
How about Sakura's training with the Diamond Dogs during the trio's training pre-timeskip? Not only does she become incredibly strong, but her training culminates with her punching the gates of Tartarus in an attempt to create a sizable dent. She puts a hole in it.