Though I could probably name quite a few items that I'd like to see, I would have to suggest the Einlanzer from Chrono Cross. Bonus points if SE still has the Masamune.

For collection purposes perhaps various trinkets from the various Square games? The pendant from Chrono Trigger, a "deck" of cards from the card games in FF8/9, a Blitzball, etc. The item descriptions (depending on length available) could even include some trivia about the item.