Although generally considered slightly inferior to its predecessors, Thief and Thief 2: The Metal Age (also available on GOG), Thief: Deadly Shadows is still a fantastic stealth game.
Now the game—colloquially known as Thief 3—is available for the first time on GOG, totally DRM-free, for $9.99. Sure, it's been available for quite a while on Steam, but it's $19.99 there. That makes the choice pretty easy.
You'll control Garrett, a capable assassin, as he battles supernatural and steampunk forces in a medieval-ish setting. The game has been praised time and time again for graphics and lighting effects that were exemplary back in 2004, and they still stand up today.
Are you a Thief fan? Which is your favorite in the series? Let us know in the comments or on Twitter.