Black Desert Online
You can score yourself a free copy of Black Desert Online, the popular MMORPG from Pearl Abyss and Kakao Games. Of course, there is a bit of a catch here.

In order to earn a free copy of the game, you need to complete the "7-day trial challenge." The challenge tasks you with getting a character to level 56 over the course of their free 7-day trial. If you do it before your trial expires, you get the game for free. It's just the starter package valued at $9.99 (USD), but it's still a free copy of the game that you can keep permanently. I just have to wonder how many people will feel a bit burnt out after rushing through 56 levels in under seven days.

That little asterisk in the above quote? Yeah, that says that this promotion is NOT available through Steam. So, if you want to participate, you need to hit up the Black Desert Online official website and start it there.