Most of the Japanese songs I like are from animes, Heres a list of my favs:

Answer Must Be Somewhere(from Rockman EXE Axess)
DanDanKokoro(DBGT)
Sabitatsu Machine gun(DBGT)
INVOKE(Gundam Seed)
Read Steady Go(FullMetal Alchemist)
UNDO(FullMetal Alchemist)
Rewrite(FullMetal Alchemist)
There\'s more, but theres too much to list:D