The battle between the Dragon Boat and the Vengeance in Magykobviously fits.
Septimus casting the projection spell in Queste to divert the Guards of the House Of Foryx from Nicko.
The fight between Septimus and Merrin in Darke. Epic dragon vs. dragon(construct) go!
In Darke, Beetle risks his life to protect the Manuscriptorium and manages to survive a good 24 hours in a small, airtight room without the charm that was supposed to help him by doing ancient breathing excercises. He was chosen as Chief Hermetic Scribe for a reason, folks.
Also in Darke, Simon, Septimus, Lucy, and Jenna are about to get into a fight, but Sarah manages to completely break this up:
Sarah: I will have no angry words in this room, do you understand? I don't care what any of you have done in the past, I don't care how stupid or misguided or just plain bad you have been - and some of you have been all of those - because you are my children. All of you. And yes, Lucy, that includes you too now. Whatever any of you have done, however much you have hurt each other in the past, when you are in this room you will put that to one side. You will behave toward each other as brothers and sisters should. Is that understood?