Killer Instinct Give-away

It looks like Microsoft have started rewarding some of their loyal customers with a free copy of Killer Instinct. Xbox 360 users have been receiving emails like the one below, stating that their loyalty has been rewarded with a free copy of Killer Instinct with all characters unlocked.

Curiously enough not all Xbox 360 Gold members have been receiving this gift. A user on gaming forum Neogaf has received it following a seven year Gold subscription and an Xbox One Preorder achievement. Microsoft have yet to issue a press release stating who is qualified for this offer.