Stage 6. Kira protects the Archangel as it descends to Earth, and depending on the player, snapping out of the sadness of fighting his friend, stopping Athrun, ZAFT and the Frost Brothers!! ... Only to be shot down to Earth by Heero the next instant.
Also, Domon plays a BIG role in this game, and does fight with NO GUNDAM, like in the series, alongside with Master Asia (Though only in the Earth stages). Here are a few examples.
Extra Session 4, "A girl in a cage". Having the Master talked to Cucuruz Doan some stages ago and Domon in his squad, attacking Nimbus in a Gundam BDII with EXAM activated, will trigger the following event: Nimbus will mock him for being in a weak Zaku II and charge at him. Domon sees Doan's morality is down and command him to fight back with the fist of his soul. As he does, he suddendly manages to go into "Meikyou Shisui" like Domon and Master, and immediatly handles Nimbus's ass to him. Thus we have the legendary "Super Zaku II" of the game.
Stage 18, "Beyond The Time". Casval(Char) reappears with his Neo-Zeon group, but ill-advised of who his enemies really are, and instead only searching Lalah's death's revenge. As both Amuro and Casval fight each other, Neo-Zeon and Londo Bell join in as Johhny Ridden and Shin Matsunaga wait for the best chance to attack in the sidelines. Kamille and Sayla both talk to him in order to convince him to join them and cease the useless battle. But only when Amuro is ready to bring the final blow to Casval, Lalah reappears in a vision, stopping Amuro's final blow and making Casval realize who his true enemies really are. All at the sound of Beyond The Time and Meguriai.
Stage 12, AU Route. TheDruggies are sent and attack. But they didn't forsee one Heero Yuy inside of the Epyon, ready to activate its Zero System. Has the player triggered the event correctly, Heero uses the System. Ass-kicking ensues.
Many instances of the Attack Combination system developed from Monoeye/DS. There are many unique combination attacks, just pick the enemies' poison. Also, the ability to recruit and position your team of mobile suits in the way you desire before eventually slashing and firing the hell out of the enemy offers many possibilities of creating such a Crowning Moment.