Super Smash Bros.
What the toys would be: Different versions of every character on the roster.
How the game would use it: While we're tempted to suggest the ability to buy characters, we think that might create some balance issues. Also, we'd run out of money. Like, literally, we'd be broke as hell. So, for balance reasons (and because we like not being bankrupt), we think different toys could be sold with alternate costumes. Real alternate costumes, not pallet swaps--we don't want to spend $4 to get a blue hat for Link. Better yet, you could store your wins/losses on the figure, letting you continue improving your ratio when you play local multiplayer at your friend's house. Oh, and there's the added bonus of being able to buy little figures of your favorite Nintendo characters, even if you don't even own a Wii U--it's win-win!