Making games is good. Free, professional software that allows you to make and sell or share your games across multiple platforms? Niiiiiice. Amazon has just released Amazon Lumberyard, a 3D game engine currently available in beta for developers who want to make things for PC and consoles, with mobile and virtual reality platforms coming soon. It's based on CryEngine, though in addition to a complete lack of any subscriptions or fees (unless you decide to use any of the Amazon Web Services) and full source code included, Lumberyard makes a pretty good case all on its own. It's also geared towards being Twitch-friendly, with features that allow you to let players chat or otherwise interact through Twitch with their viewers, or even invite others to play in multiplayer set-ups through it. Though still in Beta, any potential tool to allow more people to create games is a good thing, and there are already plenty of tutorials on the forums, though time will tell how well Amazon Lumberyard actually stacks up against its competition once developers really start digging into it. It's a 10GB file, not including some free asset packs, so clear some space. If you need me, I'll be over here getting a head start on dreaming up all the projects I want to make that are far beyond the reach of my current skillset and experience. You, though? Get started!

Windows:
Get the free full version

Mac OS X:
Not available.
Try Boot Camp or Parallels or CrossOver Games.