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 :(
May be a little off from what you’re asking but one of my favorite games period is Bookworm on the GBA. It was originally a flash game but when it came to GBA you could save your progress. The music was so cute and the sound effects were just awesome. They tried to bring it to the DS without that music and the effects and it just didn’t work. Other iterations exist as well, none as cool and enjoyable as the GBA version. I’m stuck emulating until someone rediscovers this neat little game and brings it to switch or steamdeck.