Tactics Advance. I just beat this. ^^ Of course, I haven't played Tactics, but I don't plan to. TA has Nu Mous, Vieras, Bangaas... It's much more well done, and balanced, battle-wise.
Plus, great characters like Babus and Mewt. Though I'm sure Tactics is a great game that I would like, I just don't think it will make a big impact on my gaming life as TA did.