Ahh I love the Gazette as well..
Other good ones include:
-Pierrot(they disbanded last year june though=(..i recommend Purple Sky, Nuclear Sky, Smiley Skeleton, Haruka, and Barairo no Sekai, cocoon,salvia, etc.)
-Plastic Tree(some good songs include: Sink, Harusaki Sentimental, Tsumetai Hikari, Baka ni natta noni-a funni cover song-)
-Luvie(Go to youtube and watch Irony Sun Light, you would love it)
-SID(though i did not listen to a lot of their songs before, I love their style^^ some good songs include Otegami, Ajisai, Binetsu)
-L'Arc-en-Ciel(J-rock phenomenom, and they are. Good songs include: Stay Away, hitomi no junnen, Blurry Eyes, Driver's High)
-Hide(ex- X Japan guitarist, dead, but his works would make you forget about that. Pink Spider and Rocket Dive is great)
-Onmyouza(a heavy metal band basing their style on a traditional Japanese feel..the female vocalist sure can sing! Kouga Ninchopo, Akkihokan, all great=))
-Miyavi(the dude can't sing, but he's lovable=)good songs include kimi ni negai wo, and Kekkonshiki no Uta)
There is much, much more..and they would all come to you once you start go deeper in it.
whee