Starting Sunday Dec. 1, 2013, Gears of War (normally a $19.99) will be free through Dec. 15th. To be clear, this is the original Gears of War as in Gears of War 1. Chances are you probably already played this game especially since Epic already gave it away for free with copies of Gears of War Judgment.
Then on Decemeber 16th, Shoot Many Robots (normally $9.99) will be free for the remainder of the month.