The Raging Stiffie incident in book one, followed-up in book two by Cayleb's reaction after learning the meaning behind it.
By Schism Rent Asunder
Cayleb and Sharleyan's first face-to-face meeting, where they try (and fail) to not think like lovestruck teenagers.
By Heresies Distressed
Charlz Doyal's banter, which doubles as the Crowning Moment Of Awesome. Cannonballs are wrecking havoc in his crews, musket snipers killed all the officers except for him, Charisians are encircling his army and what's the biggest problem?
All right boys, they wrecked my hat and that pisses me off!
A Mighty Fortress
The friendly rivalry between the Empire's twin capitals of Tellesberg and Cherayth, in which Tellesberg gloats that Cayleb and Sharleyan's child will be born in Old Charis (Take that Cherayth!) while Cherayth gloats that the child was conceived in Chisholm.
"Ahbraim Zhevons"'s "peculiar negotiating style." He's having way too much fun.
Sharleyan's arrangements on the day she gave birth. Why lead obstetrician of Tellesberg is on the other side of town? Midwife from another order was supposed to be in the palace, so why bother him? So why is the midwife in the city dozens of miles away? Well, the obstetrician was supposed to be there, so midwife can visit her family... right?
Cayleb: You do realize that you're probably the only empress in the world who arranged everything as to have no help before giving birth to her first child?
How Firm a Foundation
Sharleyan's telling General Hauwyl Chermyn that he's about to become the next Grand Duke Zebediah. Particularly the fact that she times the actual announcement for the moment Chermyn's about to open the door to her carriage for her, just so she could see the look on his face as the news hits him.
Almost all of Merlin's actions in Delferahk. He is having way too much fun. First off, he climbs three stories in full armor to Princess Irys's room, waits there for a minute or two, then casually clambers in the window, surprising everyone inside and leaving Earl Coris in Stunned Silence, all while stroking his Badass Mustache.
Later, when a group of Delferahkan armsmen come to the door, Merlin goes to meet them; still wearing his Charisian Imperial Guard armor. They too, are stunned completely silent. For reference, these armsmen are in their own castle, several thousand miles from Charis, and Merlin just walks out in his Imperial Guard armor, calmly introduces himself, and chats with the forty armed men standing in front of him. Then, when one of the Inquisitors demands that the armsmen attack Merlin, all he does is shake his finger at them like a "chiding tutor"
Merlin: "Let me see. Surrender, and be tortured to death later for Clyntahn's amusement, or die now, seeing how many of his inquisitors—and their flunkies, I'm afraid, Colonel— I can kill first. Let me see, let me see. Which one should I choose...?"