The entire first half of episode 1, when the idols put on their performance while being attacked by military tanks and riot forces. Especially if the viewer was expecting a normal slice-of-life show, and then got an amazing futuristic action sequence instead.
Episode 9: Coordinated Multiple Concerts as a decoy for the main event.
Episode 13 in its entirety. No, seriously. The awesome is so widespread in the episode there is no way to pick and choose among it.
Yuuko defending Akibastar and becoming Center Nova in episode 21, even considering how she Disappears into Light at the end.
Also, in episode 21, Mikako showing why she's the best pilot in 0048's history.
A meta one considering the licensing issues that affected all of Kawamori'spreviousseries in the same genre, this series got a full English release, including simulcasting on Crunchyroll.note Helps that Harmony Gold was not ever involved...