The dance scene in the Revolutionary Girl Utena film Adolescence of Utena. Simply amazing.
I uploaded this to show the grandiose surreal design of the film, although I'm left with the bitter taste of uploading such disembodied scenes failing to convey their meaning without the context of the whole film (and series). Since around 2/3rds in the entire anime becomes just one giant pile of surreal, brilliant allegories while an instantly recognisable plot is devoured by a metaphorical firework.