They also have Remnant: From the Ashes, and the Alto Collection up for free over at Epic Games right now.

Serious Sam: The First Encounter is free on gog.com

Magrunner: Dark Pulse, free on Steam until tomorrow.
SudokuT, free on Microsoft Store for 4 more days.

Slain: Back From Hell, free GOG key for signing up for the dev's newsletter. https://mailchi.mp/digeratidistribution/akuparaoffer

Hitman and the Shadowrun collection are free on the epic games store for a week!

Destiny or Fate, free on Steam for 1 day.

Free on Epic store:
-Borderlands 2 : Commander Lilith and the Fight for Sanctuary DLC

Free on uPlay store:
-The Division
-Far Cry 3 (if you're willing to jump through some Chinese hoops)
--> Worked for me, but not for someone else I know
--> In the mobile version of the Chinese website (on phone; or on PC shrink window until it becomes mobile; or on PC set the tab to mobile mode - diff for each browser), go to the Far Cry 3 page, try to redeem, sign in, verify if necessary, redeem, should appear in your account.
--> People have said Firefox and Chrome work. Firefox worked for me (CTRL+SHIFT+M for browser mode - for Chrome it's CTRL+SHIFT+I and changing the device mode). Incognito mode does not allow it to work. Perhaps some pop-up/content blockers may stop it. Perhaps chrome auto-translate may stop it. If it asks you to switch to your country's page (hard to tell if you can't read Chinese) or the international website, it won't work from there.

~~Below are free with the relevant subscription.~~

Free with Playstation Plus
-Street Fighter V
-Player Unkown's Battleground

Free with Twitch Prime
-Autonauts
-Tiny Troopers: Joint Ops
-Outcast Second Contact
-Effie
-Pumped BMX Pro

Into the Breach is free on the Epic Games Store for the week!

Railway Empire and Where the Water Tastes Like Wine are free on the Epic Games Store for a week!

Football Manager 2020, Stick it to the Man! and Watch Dogs 2 Standard Edition are free on the Epic Games Store for a week!

Rollercoaster Tycoon 3: Complete Edition is now free on the Epic Games Store for a week!

Pikuniku is now free on the Epic Games Store for a week!

ABZU is free (again) on the Epic Games Store for a week, along with Rising Storm 2: Vietnam!

Just a word of warning on Rising Storm 2 Vietnam in the off chance you actually install and play it.

There exist servers that open up a web browser automatically and re-direct you to either porn, malware, or some other unwanted nonsense.

If you want to learn more, search for info about RS2 Vietnam's "MEGA SERVER" issues.

@dhobo that's a shame, it's not on gametracker yet either so redirect servers can be a issue (CS 1.6 has that problem too).

Still a good game just be careful, generally multiplayer games have an option to view players, if they all have the same play time or not score they're bots.

sonic the hedgehog 2 is free on steam right now

https://twitter.com/SEGA/status/1316740611253313537?s=20
Nights into Dreams

Amnesia: A Machine for Pigs and Kingdom New Lands are free on the Epic Games Store for a week!

As part of Segas's 60th they're releasing free mini games that'll only be available for a limited time
Armor of Heroes https://store.steampowered.com/app/1368440/Armor_of_Heroes/
Endless Zone https://store.steampowered.com/app/1368450/Endless_Zone/
Streets of Kamurocho https://store.steampowered.com/app/1368430

Europa Universalis 2 is free on GOG
https://www.gog.com/game/europa_universalis_ii

Costume Quest 2 and Layers of Fear 2 are free on the Epic Games Store for a week!

Blair Witch and Ghostbusters: The Video Game Remastered are free on the Epic Games Store for a week!

Ghostbusters was fun back when I played it on ps3. Looking forward to giving it a whirl again.

Kingdom: Classic is free on Humble Bundle!
https://www.humblebundle.com/store/kingdom-classic-free-game

PS+ ps4 freebies for Nov are up. Hollow Knight Voidheart Edition and LOTR Shadow of War

Bugsnax (ps5 only) will be available to claim when the ps5 launches later this month.

Dungeons 3 is free on the Epic Games Store for a week!