Arsis is great, but they aren't deathcore imo.
Job For A Cowboy is Deathcore for girls, sorry
The Faceless
I LOVE them!!!!!
Ion Dissonance - Okay, but too much core for my taste...
All shall perish - I hate them, too much core and too much slam
TTEOTD - they are allright
Psyopus - Not for every moment because of the weirdness
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Some of the bands like The Faceless are more Technical Deathmetal to me. And if you're interested:
Decrepit Birth!!!!!!!!!!!!!!! - my absolute favorite Technical DM band at the moment:
http://www.myspace.com/decrepitbirth
Beneath the Massacre - ok, they're pretty coreish
http://www.myspace.com/btm
Psycroptic - more Technical Deathmetal than Deathcore:
http://www.myspace.com/psycroptic
Cephalic Carnage (great live band) - TDM with Grindcore:
http://www.myspace.com/cephaliccarnage
and @the losers: STOP mentioning pathetic keyboard-using ass-bands like Cradle of dogshit in this thread.