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 :(
Mine is Dark Cloud. It was a PS2 launch title (or near enough to it) that was sort of a PlayStation answer to the Zelda franchise. Along with the original Spyro trilogy, Dark Cloud was by far my most-played game back in the day. It had an absolute banger of a soundtrack and a few pieces of really interesting unique gameplay including an RPG element where the primary progression system was not in your characters, but in upgrading your weapons, and a city-builder where you have to place all the people in each village near or away from various other elements in the village to meet their needs.
I almost never hear anyone talking about Dark Cloud, but extremely randomly one of the like four Twitch streamers I actually watch (all of whom are Age of Empires streamers, because that’s basically all I watch these days) happens to play its soundtrack frequently on her stream as background music. So that’s been really fun.