Carpe Noctem. The way the singing, music and dance combine to tell the story of Alfred's dream is just fantastic. In addition, it really gives the ensemble chance to shine since none of the main characters (except Herbert and Magda) are active participants.
Totale Finsternis - the love duet with the right mix of curiosity, lust, fear, giving oneself to the darkness despite it and maybe, just maybe, understanding and romance between the two participants. The portraits singing in the background and watching Sarah's entrance into the castle add to the atmosphere.
Wahrheit - It's just as awesome as it is hilarious, since it has Professor Abronsius priding himself in being an Insufferable Genius, while singing at an incredibly fast pace. In fact, he sings so fast that Magda, Rebecca and her husband begin to speed up their chores to match the professors pace. Complete with an unexpected very high note by Abronsius himself.
"Finale 2. Act" - Yes, the vampires win, nearly every main character is one of the undead, but it's hard not rock along to the music of Jim Steinman's "Tonight Is What It Means To Be Young". Similar to "Carpe Noctem", the ensemble (as well as Herbert and Magda) really gets to show off again.