Rimone, at about nine years by far the youngest of the Sybilla, learns that flying a Simoun goes better when the two pilots like each other. She then kisses her co-pilot Dominura on the cheek when meeting her in one of the ship's hallways, asking if she likes her better now. That's just so cute.
Rodoreamon softly whispering "aaeru" at Mamiina's funeral later in the series, and her hairstyle in the series finale.
Don't forget Rodoreamon and Mamiina's dramatic reconciliation in episode ten. Mamiina was finally accepted as one of the True Companions in a truly heartwarming fashion.
"We were all maidens once."
Mamiina's self-sacrifice to protect a group of foreign priestesses she didn't know, who had recognised her as a true Sybilla. "Now, in your language..."
Last episode, Rimone whispering "Aaeru" as the simoun flies over head. When asked what it means? The greatest love of all.
Paraietta and Neviril's second dance, especially when Paraietta reveals she's chosen to stay a woman, instead of feeling obligated to turn into a man for Neviril's sake.