This would help a collector quickly track which games on their collection page are increasing or decreasing in value. Would be good to add to a sellers listing as well.

There are a lot of results in the eBay Game Sniper tool that are incorrectly matched. For example, a listing explicitly stating it's for the Xbox 360 version of a game being matched to the Xbox One version in the tool. Listings for demo discs and loose manuals are also often matched as the actual game. If refinement of the tool is planned in the future, it might be beneficial to start compiling a database of matches flagged as incorrect, which we could add to by using a "report" button.

Add One Piece Japanese TCG 

Please add support for PAL PC games or add PEGI and 13 digit UPC support on NTSC PC games. Thanks!

Create a tool for users to create a custom set or list.  Then let users collect against that list and see what they have in their collection and what they don't have yet.

Examples: a list of all licensed NES games, Mega Man home console games, games published by Konami, etc.