Battlefield Heroes
This tongue-in-cheek parody of the plethora of deeply-serious World War Two game is not only hugely fun, but also an interesting take on where big companies like EA might take their business model in the future.
While BFH has a micro-reward system all of the game-changing mechanisms, such as weapons and equipment can only be unlocked through playing the game. However, more cosmetic aspects such as appearance and emotes can be purchased using a micro-trade model.