US/North American versions, and complete (box + manual) unless otherwise noted. Some I'm not sure if they're that rare, but I'm writing them just in case (marked with a *).
Saturn:
- Panzer Dragoon Saga
- Radiant Silvergun (Japanese)
- Burning Rangers (EU/PAL)
- Guardian Heroes
- Dragon Force
- Shining Force 3 (Scenario 1)
- Shining the Holy Ark *
- Legend of Oasis *
PlayStation:
- Suikoden 2
- Suikoden 1 (disc only in jewel case... but I printed the original Japanese cover so it looks better than the retail US version ^^)
Other:
My boyfriend owns the following on SNES, carts only, dunno how much those are still worth, what with the countless ports and re-releases:
- Chrono Trigger
- Final Fantasy II (IV)
- Final Fantasy III (VI)
I also have FFTactics, Breath of Fire 3, Xenogears, Castlevania: SotN and Silent Hill for the PS1, which I recall were worth quite a bit on eBay (though not in the same amounts as, say, Panzer Dragoon Saga) before their PSN re-releases, though Suikoden 1 seems to be worth a bit still. Then again, I imagined the HD release of Guardian Heroes on XBLA would also lower the prices for the Saturn version, but they're still morbidly high on eBay...
Edit: oh yeah, not to brag, but I didn't pay a particularly high price for any of those, because I'm not a collector, I have these games because I wanted to play them and I love them (well, except Xenoblade... >_>). I mostly got them shortly after they came out. The exceptions are some Saturn games which I had trouble finding in stores at the time even when the Saturn was still active, due to Sega of Canada's atrocious distribution and the pre-Internet era, so some of them I got off eBay but still managed to find decent deals (Shining Force 3, Dragon Force), and there are 4 of those games that I bought off a friend who was getting rid of his game collection for a stupidly low price (I felt so bad I told him he'd make a lot more money on eBay, but he insisted on selling them to me since "money isn't important, besides you'll enjoy and appreciate the games more than I did", were his words): Panzer Dragoon Saga, Radiant Silvergun, Shining the Holy Ark
and Guardian Heroes for... $45 USD, shipping included. Not each, mind you, but
total. I got soooo lucky. xD