Pretty much what other people have said and...
Porno Graffitti (spelled like that) - So different and awesome, it's hard to to put them into a genre.
Favorite song: Uzu
http://www.dailymotion.com/visited/search/...i-uzu-le-remous
B'z - Awesome, Awesome J-Rock, one of the first bands I heard from Japan. I can't name a favorite song because they have so many.
The Alfee - Have been around forever. Strange Rock/Pop/Folk hybrid, but it works. In fact, I just ordered their single collection from YesAsia.
Not really my favorite song, but it shows how awesome their lead guitarist, and towards their end, how awesome their accoustic guitarist is:
http://youtube.com/watch?v=_kbJt6ZxGsk
Also, Southern All-Stars, Tomoyasu Hotei, LOW IQ 01 (good luck finding anything on him) all rock as well.