Chopin etudes are great. Black Key and Revolutionary (no matter how much they are played), they always have a positive effect on non-musicians. Chopin is probably one of the more accessible composers to non-musicians; nocturnes, preludes, ballades, everyone loves them.
Rach etudes too... probably the op 33, and the more tonal etudes out of the op 39 I'd say. The two D minor etudes had a good effect when I played them. His preludes are good too.
IMO the Revolutionary Etude is the perfect crowd pleaser... musicians are probably sick of hearing it, but non-musicians love the intensity of it.