There were a ton of times I had to stop reading because I was laughing at humor or gleefully chortling at the action...but I think this series of lines sticks out as my favorite.
Grimm strode toward the Spirearch’s Manor, his booted steps striking the stone floor with sharp, clear impacts, and reminded himself that murdering the idiot beside him in an abrupt surge of joyous violence would be in extremely bad taste.
“A tad stuffy,” Rook said disapprovingly. “Might as well call you ‘Captain’ all day, as though you still had a true commission.”
Extremely bad taste, Grimm thought. Appallingly bad taste. Historically bad taste. No matter how joyous.
The smile vanished. “I will have that core crystal, Grimm.”
Grimm nodded thoughtfully. And then, quite quickly and with no restraining gentleness whatsoever, he slapped Commodore Hamilton Rook across the face.
Rook’s eyes blazed and he drew himself up to his full, intimidating height. “You arrogant insect,” he snarled. “Do you think you can slap me about without paying for it?”
In answer, Grimm took a quick step forward and did it again. Rook tried to flinch away from the blow, but Grimm’s hand was too quick for him. Again the sound of the slap echoed down the hallway.
“Sir,” Creedy said, “the estimate for repairs is . . . considerable.”
“I’m aware,” Grimm said.
“I’m afraid that . . . times being what they are, there might be those in the High Houses who might begin to put pressure on you to sell.”
“Really?” Grimm said. “Well, I suppose they have the right to make offers.”
“I’m afraid they might be more aggressive than that, sir,” Creedy said earnestly.
“If they get out of line, I’ll just slap them around and threaten them until they stop,” Grimm said.
At that Creedy all but spat out some of the drink he’d just taken. He managed to choke it down and after a moment managed a chuckle. “My sister told me you had an odd sense of humor, sir.”
“I suppose I do,” Grimm said.
Although...this one is a close rival:
She watched his hollow, weary eyes stare for long heartbeats at the scorched not-men who now littered their library floor before he answered. “What have we learned today, Folly?”
“That one ought not to use etheric weapons against an etherealist?”
“While what you say is very true, I was hoping for a different context.”