If you're a GACKT fan then you probably know of MALICE MIZER so I'm not going to suggest them like I usually do to people who ask for Jrock~ XD You must have heard of Versailles as well?
Exist † Trace (awesome all girl Visual Kei group)
V-last.
D=OUT
vistlip
And (My current favourite rock band)
lynch.
NIGHTMARE
A(ACE)
BORN
ScReW
-OZ-
Mix Speaker's, Inc.
Onmyouza
Girugamesh
12012
ViViD
lolita23q (two videos because they have a new singer now, so the first video is the old singer and the second is the new singer)
Kiryu
That's everything I can think of off the top of my head. XD I kept thinking of lots of Oshare Kei bands but I didn't know if you wanted some of those either~