We already gotten used to see Humble Bundle offering, every now and then, a free game. Even now, on the Humble Store, you can get activation codes for Steam for the third person shooter Spec Ops: The Line, developed by Yager Development and published by 2K Games in 2012.
Spec Ops: The Line tells the story of Captain Martin Walker which, accompanied by his Delta Force team has to return to Dubai to save a Colonel of the U.S. Army. Two main concepts sit at the base of the gameplay: the possibility of issuing orders to your team as well as the field, sand storms having the possibility of changing the configuration of the battlefield.
However you need to worry because Spec Ops: The Line will only be free on the Humble Store for just one day and a few others.