Guild Wars 2

Wouldn’t it be cool if you could collect trading cards in game, and maybe even play a mini game based on those trading cards? It may even act as an incentive to do random stuff in the game (as random rewards), such as when you randomly get silver doubloons in jumping puzzle chests, and maybe trade them in for items or use them as a components in the mystic forge. Maybe you can use art by the community? Maybe make a fan art contest and the artwork of the winners will be used for the cards?

In a strange sort of way, tonics could be considered a form of “trading card” in this game; you can trade (most of) them, battle with them and get rewards (well, achievements) for doing so.

If they reintroduced polymock (from GW1), your idea could be perfectly applied to it. It would be pretty neat.