This April, Rusty's Real Deal Baseball will be released in the eShop. It's a baseball game where you...hit baseballs, no big deal there, but the way you buy the game is pretty nuts.
See, you download the main game for free. The minigames you play within, though, you have to buy. Nintendo gave an example price of $US4.00 for one of these titles, but that price isn't locked down.
Instead, you can negotiate the price, by offering an in-game character certain items. If you offer something they like, then the actual price, in real human money, comes down.