First, Grieg's one and only Nocturne. Pity he didn't write more. I think he had a knack for 'em.
Next, a little finger-bender I like to call Schubert's Impromptu in A-flat. It's seven minutes of pure hell on the right hand, and the left don't get off all that easy either. I can usually only make it through this piece once before I need a break, so I had to use my first take, despite a few minor errors on my part.
For an added kick, plug in your sub-woofer speakers and blast the shit outta this song around the 2 minute mark when he switches into C# minor. Angry little Franz.