
If you preorder XCOM on Steam, you can help unlock exclusive XCOM-themed bonuses for Team Fortress 2. If there are enough preorders the three bonuses will be unlocked. Also, if there are even more pre-orders Steam will give you a digital copy of Civilization V. The site also states that if you already own Civilization V, you can gift your free copy!

Amazon Prime subscribers can claim free PC games to keep via its Luna service.

XCOM: Enemy Unknown rebooted the series back in 2012, and has since inspired numerous new strategy game series to be born.
If someone gets into this I'd recommend getting the enemy within version. It's got all the dlc included so it's the better version. Wish the author would've atleast mentioned it. I didn't see it.
Fantastic game though. Xcom 2 is top notch also. I've spent countless hours in these games.

There are few things more gratifying in gaming than skillfully turning the tide of a conflict. And few genres provide as many opportunities to abruptly reverse the odds via skill and forethought as tactical strategy. To be sure, we are more often than not talking about turn-based tactical mobile games, specifically titles in line with the iconic landmark series (XCOM and Jagged Alliance) that made the genre a genre.