Casanova's reply upon being accused of having sex with a novice (meaning a nun):
Casanova: Well, she was hardly a novice.
When said novice was confronted by the inquisitors chasing Casanova:
Dalfonso: Eternal damnation for one night with Casanova. Sister Beatrice: Seems fair.
Casanova's attempts to maintain a civilized, sophisticated conversation with Francesca, her mother, and his future father-in-law — while his young, sex-starved fiancée is under the table.
Giovanni is making quite a name for himself in the local brothel, tying up (not like that) all of the prostitutes at once. In the lobby, a waiting john asks of the madam, "Um, when is my turn?"
Giovanni keeps slapping Casanova and throwing his glove down to challenge him to a duel. Lupo keeps picking it up and handing to Giovanni, allowing Giovanni to continue slapping Casanova. After the third time:
Casanova: Are you two working together now?!
Inquisitor Pucci claiming "Witchcraft!" to Casanova's hot aired balloon flying, then his assistant Andolini tries to correct him by explaining it with accurate science only for his boss to give him a Death Glare.
In the opening scene where Giacomo is being chased and he plans his daring escape out the window onto his horse. Only to land right on his butt and give out a disappointed "Bollocks!" before said horse to just run off leaving him behind.
There is also this line at the bridge:
Giacomo: You love your wife, I love your wife. Aren't we both on the same side?
The look on Giacomo's face when he finds out that Bellino really was a girl is just golden. Also this line: