Halo 4 for XBox drops to $39.99 at Amazon. That's $20 off the release price from just over a month ago and $10 less than we found it anywhere else. Plus, it ships free and comes with a $10 Amazon Instant Video Credit which will be emailed to you following your purchase. This highly-rated game on myriad gamer's Christmas lists can be enjoyed by up to three players at a time. Amazon prices change like the wind so grab it quick if you're interested. Sales tax is not charged in most states.