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. 🙂
Edit 2: It has become too much for me and I have to disable notifications. Thank you for the massive response and please continue to discuss with everyone here. ❤️ 🫡
Right now I’m really hooked on Lucky Tower Ultimate. I’ve never been this into anything like it before, roguelites mostly bore me, but this game has such a goofy charm and - for an Early Access game - surprisingly deep explorability. It’s my go-to game for picking up my Steam Deck and screwing around for 20 minutes or an hour. I’m still having a ton of fun with it.