In my campaign, the "One Must Die" chanting at the Death House ended up becoming a recurring theme. At one point, Strahd had surprised the party by setting up a tea table and umbrella in the road intersection south of Krezk. There, he wove the phrase "One must die" into conversation as a signal for one of the PCs, secretly a traitor, to attack the party. It was fun.
Strahd had some other good lines during the St. Andral's Feast encounter in Vallaki. Strahd, in disguise as Vasili von Holtz, gave a cool sermon (which I ad libbed on the spot, because who preps, right?) on the charity and mercy involved in putting a suffering horse out of its misery. The players, correctly deducing that it was really Strahd, were all like "Oh crap, he's going to kill the congregation!" For the record, they were able to save half of the people at the feast.