Halo 4 for Xbox 360 FREE thru Microsoft App Builder Rewards NOT A DOWNLOAD
Go to https://build.windowsst
Once you have created your account, do as many of the "Quests" as you can without actually creating any apps and you should have accumulated 3000 points total. This will require that you do the "Student" quest where you change your profile to say you are a student and choose your "school" from a list. You can always change your profile back after earning the points. Basically, use the black navigation bar on bottom of page to find any Quests you have not done already.
Many of the Quests make it sound like you actually have to follow through with something once you go to the linked site, but I got my bonus points by going as far as I could without doing anything major, then returning to the main site (you should then see your bonus total increase).
One of the Rewards is Halo 4 for Xbox 360 for 3000 points. If you do not want this, you can wait to try to earn 500 more points to get a free copy of Windows 8 Pro Upgrade.
Credit goes to kkiran