If you liked the older Call of Duty games, but wanted something a bit grittier with a faster time-to-kill, Insurgency can be good fun. It's also free.
That's the case for the next 48 hours, anyway. To mark the release of Insurgency Sandstorm, the developers are letting users add Insurgency to their Steam library for free. You'll be able to keep the game for life, provided you "install and play" the game during the free window.
As for Insurgency itself, here's some videos to give you an indication. The short version: think of the Hardcore mode from Call of Duty: no killfeed in most servers, a much slower pace, guns with lots of weight, and a huge focus on teamplay.
Insurgency: Sandstorm launches on PC next month, and will come to console next year. To add Insurgency to your Steam library, head here or navigate to the game page through the Steam client.