FREE - In Google Play
FREE - in Win Phone Store
I mean like the trophy showcase that we've already got.
The way I thought about it we'd have a "My best games" box on the right side of our profile page with links to our 3 or 5 best games. We could add a new game to it with one more option just after it ends (next to "Computer Analysis", "Give a Trophy" etc).
I know we have the "best win" feature as of today, but it frequently has bad games won on time against someone rated much higher than you.