Feel welcome to recommend some free games and/or mods for other people to find.
I'm not talking about games that temporarily go free though - they need to be always free (or have become permanently free).

I'll start, but all of my recommendations are for Steam:

Games:

Dr. Langeskov, The Tiger, and the Terribly Cursed Emerald: A Whirlwind Heist
https://store.steampowered.com/app/4...irlwind_Heist/

Heroine's Quest: The Herald of Ragnarok
https://store.steampowered.com/app/2...d_of_Ragnarok/

Cinderella Phenomenon
https://store.steampowered.com/app/5...eVisual_Novel/

SC2VN - The eSports Visual Novel
https://store.steampowered.com/app/4..._Visual_Novel/


Mods:

Portal Stories: Mel (Portal 2 Mod)
https://store.steampowered.com/app/3...l_Stories_Mel/

That's all for now.