Brahms' Haydn Variations has a wonderful two piano version written by the composer himself. I just heard Argerich and Freire perform it last Sunday. It's a great two-piano piece if you love Brahms, which I do.
They also did the 2nd Rachmaninoff suite, Ravel's La Valse, and the Lutaslawski Paganini Variations (very much a show-off piece). The Ravel is brilliant and very difficult. The Rachmaninoff is, well, Rachmaninoff -- written about the same time as the 2nd concerto, so if you like that, you'll probably like this suite.