Simmo8591 said:
I have the original (non platinum) copies of ff7,8,9,10,12 and the ff12 hardback guide that only came with a preorder.... probably not that rare now but in 30 years that guide may be worth something...
Ahh, I got all that. I love my hardback guide too, would miss out on so much were it not for it. (keep the faith it'll be worth something someday

)
As for my own shining gem in my collection,
Monster Rancher on Playstation. Now that game was RARE! took me a year to track down a copy, can't imagine what someone would pay for a mint copy now. (awesome game btw, you can create monsters by letting the game read info about any music CD/game CD - every CD you have will have a unique monster, pretty awesome)