Twitch Prime members (Amazon Prime users who connect it to their free Twitch accounts) can get a pack of games from Digital Devolver including Hotline Miami 1 + 2, Broforce, The Messenger, and a few more I'm not as familiar with (STRAFE, Crossing Souls, & The Swords of Ditto). Outside of maybe Hotline Miami 2, the first group I named were all pretty much in the Indie Game of the Year type category the year they came out, including The Messenger just this year.
Subnautica should also be on its last day of being free on the Epic Games Launcher. Super Meat Boy will become the platform's new free game either today or tomorrow.