Fatshark are giving away 100,000 free Steam keys for their 2010 multiplayer, class-based shooter Lead and Gold: Gangs of the Wild West. This is (one of) the games they made before the Skaven-tastic Vermintide, and it appears this is an effort to get people playing something from their back catalogue.
In order to get one of the keys (assuming there are any left at the time you’re reading this), head over to this site. It’ll request your name and email address, but I’d imagine you can make up a name if you really feel like it.
It’s noted that Steam keys may take 30-60 minutes to show up in your inbox (and suggests keeping an eye on your spam folder). After redeeming that key, you should be all set to play Lead and Gold for free.