Super Robot Taisen Original Generation 1 and 2 both for the Gameboy Advance (but you can probably just download then in a cellphone emulator mhnnhnhn).
Two great tactical RPGs featuring giant robots, good animation, awesome and funny characters, amazing music and a quite intriguing story. The first one doesn't have all that good animation quality, but the second... *whistle*. I still recommend you play the first game just to get to know the characters, since even in the first game, the character building is still very good. But play the first stage of the second game, just so you can have something to look forward too.
Here, one of the songs of the games. There's many more in the first, and the second has all the best ones.
(a tip, use headphones when listening to the music, your left and right ear will both appreciate their respective parts)