When looking for L'Arc~en~Ciel, remember the funny waves; sometimes they are there, sometimes not.
Also try:
Gackt - solo artist and he first sang for Malice Mizer
Kagrra, - they are disbanded but their albums are rather good
BUCK-TICK - started out as a hard rock band but now play with all sorts of sounds and themes
é›…-MIYAVI- -interesting guitar style
T.M.Revolution
exist†trace - they may look like guys but they are all girls