For me, Tunic. Well, it's a bit more complicated. I was burnt out on soulslikes and wanted a break. Saw what I thought was a nice little Zelda clone, as in I was scrolling the Steam store home page and did a double take when I saw the one and only piece of promotional art for the game. That character design looked like it was one floppy green hat away from a lawsuit from Nintendo. Instantly downloaded it upon learning that the instruction manual played a big part in the gameplay.
I have fond memories of game manuals when I was a kid, coming home from not-yet-gamestop with a new game looking at all the concept art, or having my parents read to me from the super mario 3 manual when I was little. Anyway, long story short the game was another soulslike. Set in the ruins of a fallen civilization? Check. Spend currency to level up? Check. Opening up shortcuts to previously visited areas as you progress? Check. Difficult bosses? Check.
Oh, but what's this? The whole game is in this indecipherable script that you have to decode? Oh baby! I spent way, way way too much time trying to decipher it. I got so obsessed that it was effecting my sleep and I had to uninstall the game for a few weeks. Never ended up solving it.
spoiler
I knew it was an English cipher from the beginning. Nobody ever goes full conlang, as much as I would love that. I got as far as deducing it was phonemic, as the same glyphs kept appearing before cleartext words, which I assumed were "a/an" and "the", and the way "the" was written made me think it was two glyphs, one for the and one for . The last thing I got before giving up and looking it up online was one of hte ghosts standing next to the well in the village and repeating the same word three times. Of course he's saying "well well well".
Anyway, overall the experience was a roller coaster of mild interest to acute dislike shifting to all consuming curiosity and finally to exasperation. I don't think a game has evoked that many varied reactions from me. The music is also amazing.