Bill: "-I want you to go out there, and I want you...to punish...the person who's responsible- *sob* - for murdering this poor little rabbit." What makes it even funnier is how quickly Bill regains his composure, with a firm "Understood?" Even funnier: the lament of a dead rabbit is coming from a butcher.
P.T. Barnum's escaped elephant running through during the Draft Riots is also rather hilarious, especially due to the Dead Rabbits' reaction.
When Monk is running for sherrif.
Boss Tweed:(impressed) That man was right born for this.
Amsterdam: He's killed 44 men, and laid low a couple hundred more.
Boss Tweed: Is that right? We should have run him for Mayor.
The Reverend's Double Take at two obvious crossdressing men among the ladies at the Reform Dance. One girl whispers before the Reverend sees him, "You shoulda shaved closer."
McGloin being smacked across the face by a bishop. Of course, he really deserved it.
"That, my friends, is the minority vote." Dark humor considering the circumstances, but still.
"Now that was bloody Shakespearean! You know who Shakespeare was? He's the fella who wrote the King James Bible!"
In a darkly comic scene, two rival fire brigades brawl out a territory dispute, ignoring the actual blaze. The two heads of the fire brigades overlook the fight and have a heated discussion over whose land they're on.
When Amsterdam introduces himself to Bill.
Bill: What is your name?
Amsterdam: Amsterdam, sir.
Bill: Amsterdam? I'm New York.
"The appearance of the law must be upheld. Especially while it's being broken."