Phantom Crash, seriously it's just mechs fighting but with more variety in what you can do, and it isn't overly complicated, it's just "fight, win money, buy more weapons, fight again" the music is amazing, and it's a brilliant game, much better than Hawken in my opinion.
KuruKuru Kururin While the name sounds weird, and the gameplay looks weird, it's actually a great game, I finished it in my childhood, and it was actually on of my favourite Game Boy Advanced games, the music, how it plays, how it looks, it was made brilliantly is decent in it's own regard. I think it was a launch game for the Game Boy Advanced anyway, so for a launch game it was great.