Medabots
4 versions (the "different" subversions (think pokemon red and blue) were nothing like demikids where a totally different game happened)
1) Medabots RPG- Only RPG to appear outside Japan.
2) Medabots RPG (shingata medarot)- more or less the same game as above although a far more "kiddy" appearance. Japanese only. I have toyed with the idea of a script port but I do not see the need when there are more pressing hacks to do.
3) medarot NAVI. RPG too with similar mechanics, a drastic tonal shift (more shonen than simple kids cartoon) from the other game and Japanese only. No translation I know of.
4) Medabots AX (medarot G in Japan). Platform fighting game (think Jump Ultimate stars but not as good and zoomed in quite a bit) and never one I really "got". Some quite like it though.
The RPG is based somewhere between the first and second series of the anime and is one of my guilty pleasures, my only gripe is despite there being hundreds of parts* they use a low number of preset combinations. Whether I redo it or not is up in the air right now.
*that probably made no sense to those that have not played it so in the game you get legs, head and two arms. The legs sort speed and terrain issues out while everything else allows a different attack.
You also have cubix (an isometric platformer (think GBA spyro)), I liked the cartoon but the game was somewhat dull.
Another similar game is robopon 2 and also worth a play.
If however you find the gamecube version I would like to hear your opinion on the subject as I never got around to playing it.