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 :(
Back in the day Hidden & Dangerous was a fantastic game. Spent many hours crawling on my stomach sniping. And the multiplayer LAN parties were epic for the sheer fun and hilariousness of the bugs we found. Only my friends at the time have ever heard of it though.