For me it was Terraria, Satisfactory, Tetris Effect Master Mode, Minecraft with Mekanism mod & CSGO / CS2 (almost 2000 hours in CS alone).
Edit: There are so many answers that I might only reply if I have something interesting to say. I will read all of your answers though. 🙂
At different times:
Luanti (AKA Minetest)
0AD
Sauerbraten
Battle for Wesnoth
Shattered Pixel Dungeon
and further back:
Action Quake 2
WipeOut 2097 (AKA XL)
Oh cool, most of them are open source and / or free as well, if anyone wants to try them.
really cool games fr