I got Killer Instinct free from MS...

"Today is apparently the day where Microsoft turns into Oprah: You get a copy of Killer Instinct on Xbox One! And you get a copy of Killer Instinct on Xbox One! And just like Oprah, Microsoft's dispersal of said free game is seemingly at random. According to the official Xbox Twitter account, the company "considered a variety of things like Gamerscore, LIVE tenure, & other factors in markets where #XboxOne is available" in deciding who would receive free copies. Codes to unlock all the characters in Killer Instinct will arrive on launch day or thereabouts following today's email blast (seen above) alerting users."