Brahms' Rhapsody in G minor is wonderful, the other one in the set is good too.
One of my favourite pieces of all time is Beethoven's Pathetique Sonata (1st movement here).
For more contemporary stuff, I can't recommend Ligeti's solo piano music enough. Etude 13 is in large part responsible for me getting into contemporary music, and thus, becoming a composer.
EDIT: Also, John Field was a big influence on Chopin; he's credited with inventing the nocturne form I think. Not as virtuosic though, if that's what you're into.
This is the monthly thread for posting media of various types that you've found that you enjoy. I find that exposure to LW ideas makes me less likely to enjoy some entertainment media that is otherwise quite popular, and finding media recommended by LWers is a good way to mitigate this. Post what you're reading, listening to, watching, and your opinion of it. Post recommendations to blogs. Post whatever media you feel like discussing! To see previous recommendations, check out the older threads.
Rules: