Microsoft is finally dipping a tentative toe in the free-to-play market with the release of Happy Wars next week. The multiplayer action game will be available next Friday, October 12, for free if you're an Xbox Live Gold member.
Being a F2P game, though, you'll have plenty of opportunities to spend your Microsoft Points. Previous announcements have touted thousands of "lavish" cosmetic items to show off your character's originality.
The Gold requirement makes enough sense--the game's focus is multiplayer, which requires a Gold subscription anyway. But the game also features a single-player campaign, free for Gold members. The implication seems to be that those without a Gold subscription will be able to play too, but would have to pay for it.