ZDoom

If you hurry right now, you can claim Sanitarium on GOG. 15 minutes remaining as I post!

Dammit! Missed it (by quite a bit). Thanks for the "heads up" though. Several of the GoG posts in this thread have been useful to me.

There are giveaways on GOG right now. There's apparently one for Shantae: The Pirate's Curse that lasts for 17 hours, and it seems Hitman: Absolution for 2 hours. At least that's what it seems; I just get a big banner telling me I already have the game and can't get another copy.

Oh, and also you can now get Daggerfall Unity: GOG Cut, so that's a convenient way to play Daggerfall with a curated selection of mods and enhancements. I figure that one will remain free.

https://store.epicgames.com/pl/p/maneater

shark simulator - you eat fish and humans. Have story mode, RPG elements, spread terror.

An isometric adventure game called Beautiful Desolation is free on GOG for the next 71 hours.

Ever wanted to play They Live as a 2D platformer on an alien planet? If so, don't miss the latest giveaway on GOG: Flashback, for the next 43 hours.

Virtuaverse, GOG, 28 hours remaining.

All of the DLC for the following games are now free on Origin due to the "Bioware Points" system used to purchase them being discontinued:

Mass Effect 2
Mass Effect 3 (excluding Multiplayer Packs)
Dragon Age Origins
Dragon Age 2