I've heard of The Pillows and the Asian Kung-Fu Generation.
I owe a "Hikki" CD, as Utada Hikaru is so lovingly dubbed by various fans that I hang out with. Since she's on your list and she's famous, then I feel obligated, if not encouraged, to devote a half minute's amount of time to promote my favorite singer...
GACKT!

Gackt Camui is one of the prettiest, sexiest, drop-dead gorgeous men... with the most fantastically orgasmic voice ever! Can we say: wow?
I also lovingly support and/or worship:
Hyde, and his band L'arc in Ciel
Hide -- in both X Japan and spread beaver
Dir En Grey
Glay -- Neuromancer is KICK ASS!
and, last, but not least, my female contribution:
BoA
Oh, and don't forget the lovely SweetS.

God bless visual kei bands and all their glorious goodness.
Heidi shook her head and sighed.
"So... what were you doing in line for an autograph then?" she ventured.
Sebetin thought about this.
"I came into the shop, and saw that there was a line. I thought I might join the line."
"And then?"
"And then I joined the line, and the line got smaller, and I met you."
- Sebetin's Ex-Lovers