Doom is one of the most well-known first person shooter series in video games, and right now Google is giving the first two games away to Chromebook owners.
Both Doom and Doom II are now available to claim on Google's Chromebook Perks webpage (via Android Police). Google says that you can get the games with the purchase of any Chromebook, but some folks report that the offers aren't showing up for them. So if you've got a Chromebook, visit that Chromebook Perks page and see if you've got free copies of Doom and Doom II waiting for you.
These are the original two Doom games, released in 1993 and 1994, and they're the Android ports of those titles. Still, these are two classic video games that helped to popularize the FPS genre, and getting them for free just for owning a Chromebook is a pretty sweet deal even if you already own them on other platforms.
Google's Chromebook Perks webpage is also offering Fallout Shelter, Stardew Valley, and The Fall of the Dark Brotherhood story expansion for The Elder Scrolls: Legends all for free, so if you've got a Chromebook and any interest in games, it's definitely worth your time to check that page out.