this thread needs more bloodthirsty butchers....
I'm also gonna throw a few more out there:
Sonic Youth - underappreciated. EVERYONE'S HEARD OF THEM, no one listens. especially Daydream Nation. Watch the tomei shoujo video. look at the manga very carefully for a sonic youth reference.

ZOMG, where did that come from!?
Spiral Chord - nakao played bass for them a year ago. sweet garage rock.
condor44
a band apart
mock orange - i don't care what anyone thinks. this band is absolutely brilliant. I am really, really surprised these guys aren't mainstream yet. they won that MTV special underground band contest thing or whatever and performed in front of thousands of people, and tour all over japan, europe, and n. america.
Primus
Beatsteaks - great German band. another band that no one will listen to. download smack smash. you won't be dissappointed.
ides of space
syrup16g
Luminous Orange
and i'm gonna go ahead and say it: radiohead. it's still pretty good, even though people bash them often cause they hear the word emo and run for the fucking hills. and death cab for cutie's earlier work isn't bad either. up until the photo album. transatlanticism was

and i hated Plans.