Mine has to be Dragon Quest: Rocket Slime, a DS spin off of the Dragon Quest series that sees you playing as a slime operating a tank and rescuing the people from your town. You run around the overworld, collecting items to use as ammunition and saving money to upgrade your tank. The art and music are just as great as you’d expect from the Dragon Quest series. It made fantastic use of the DS’s dual screens. It’s also written for a younger audience, so a lot of it is just really silly and fun! Try it out for sure, I’m so sad there’s no sequel :(
This is kind of obscure but I used to love this MMO rhythm game called Audition Online, published by Nexon in 2007. It’s completely deserted now, hasn’t been updated in years, and only runs on Windows OS, but sometimes I’ll revisit it and play for hours despite only like 10 people being online lol