I had to sell a majority of my old/good stuff some years ago during a lean time, but managed to keep a couple goodies:
Panzer Dragoon Saga (orig. US release, preordered that sucka)
Guardian Heroes (US release)
I've also still got Guardian Heroes JPN release, but that's not nearly as rare as the US one afaik.
I still sorely miss most of my Saturn collection, but haven't had the heart or the cash to rebuild it.