Cytus
Pokémon Platinum
Diablo 1
Mabinogi
Yume Nikki
Cytus is pretty much the core of my whole personality (and music taste) so it is The Most Defining game for me. Platinum is special since it was my first game instead of a family game or whatever. Diablo scared the crap out of baby me but I really liked playing it! It was something my entire family played, everyone had a character save. I always was interested in MMOs but Mabinogi is The One that works for me. I reminded me a lot of Runescape when I played it but didn't have an egregious pay wall behind half the content (when I got to playing mabi, ik they had some pay walled stuff that they've gotten rid of over the years). I play any tab target MMO and I'll just have 'damn I'd rather be playing mabinogi rn' in the back of my head most of the time. And Yume Nikki was my first real foray into horror. I'm a wimp and hate playing horror games but I loved how vague everything was that I learned everything I could about the game. Enough to guide a friend through it over a phonecall.
NOOOO DON'T EAT THE TOADS