Radiohead
No Doubt
Karnivool
The Butterfly Effect
Nirvana
Atreyu
The Distillers
Explosions in the Sky
Finch
Further Seems Forever
Lost Prophets (Start Something era)
Orgy
I checked out Gazette and Penicillin and they kicked my ass, even though they're slightly hardcorish too. That's mitigated by the thick cloud of Japanese awesome about them.
Also, the new L'Arc~En~Ciel kicks unholy ass. The 2nd track, Pretty Girl, is the catchiest shit I have ever heard.
Gackt is pretty good but not really my thing. GazettE is hard-corish, in a bad way, just like, say .lynch, never really got into them. dir en grey is really good IMO.
Miyavi is an awesome guitarist but he looks and behaves homosexual and I don't like most of his songs ("Selfish Love" is awesome tho, IMO)
I think you should check out Alice 9, Lolita23q and Serial Number, they're pretty good. I also like stuff like Buck-tick, Blood, Phantasmagoria.
The only band that dresses as anime charas that I know of is Himitsu Kessha Kodomo A