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Morrigan- Poison by Alice Cooper Because you know its true XD
Im So Sick by Flyleaf

Bullet-Pogo by System of a Down

Heatstroke-This Fire Burns by Killswitch Engage

Cold Snap- So Cold by Breaking Benjamin

Heartstroke/Reaper-Kick Some a** by Stroke 9

also:

If You're Into It -by- Flight of the Conchords
http://www.youtube.com/watch?v=pY8jaGs7xJ0

Ladies of the World by Flight of the Conchords
http://www.youtube.com/watch?v=hFjrbmj0CUc&feature=related

Tara and Kyle: Secret Smile by Semisonic
http://www.youtube.com/watch?v=l-yQdNjC3AY

Victor and Ricky - Down and Out by Tantric
http://www.youtube.com/watch?v=PceURS0toUs

Tara Illias - Fall Down by Tantric (I've actually kind of always attached a unconscious bayou blues/harmonica background music for Tara (sort of like how certain sounds or instruments get assigned to characters in stage plays). Sort of bad a**/cool vibe)
http://www.youtube.com/watch?v=_z-pqfSs_8E&feature=related

Danny - Head Down by Sound Garden
http://www.youtube.com/watch?v=0d7xVfxvzZA&feature=related

Serena - Hollow by Submersed
http://www.youtube.com/watch?v=JuFsqR_3r28

Sasha's clones - She by Taproot
http://www.youtube.com/watch?v=yhqyO91v1b0&feature=related

Christian - Shadow On the Sun by Audioslave
http://www.youtube.com/watch?v=jiqVcEiL90Q

Ricky - Pardon Me by Incubus
http://www.youtube.com/watch?v=EyfO1-zSd7M
(I find it hilarious how the lyrics concerning flames in this song work on both their intended level and a literal level with Ricky)

Victor and Ricky vs Christian - Megalomaniac by Incubus
http://www.youtube.com/watch?v=iFnnV595byE

Blake - Survival of the Sickest by Saliva
http://www.youtube.com/watch?v=zlzcrKYYuvc

Belial - Fade to Black by Metallica

Chamerlain - Sharp Dressed Mad by ZZ Top

Stifle - Decadence by Disturbed

Syren - Symphony of Destruction by Megadeath

Danny - My Friend Misery by Metallica

Belial and Seraphael - Out of My Way by Seether
http://www.youtube.com/watch?v=FBpZk1xzm4c

Goddess - The Theme Song for Captain Planet

HUNTERS (the entire group)- Blam Blam by Killer Mike
(Just picture the refrain playing while they all walk in slow mo down a street.....yeah, that's the stuff.)
http://www.youtube.com/watch?v=3f_rWDU_iG4

Cryptic - Third Eye by Tool
http://www.youtube.com/watch?v=2EIQpdbwE8Q (part 1)
http://www.youtube.com/watch?v=ZR8gulUKr3Y&feature=related
(part 2)

Marionette - Master of Puppets by Metallica (can't believe no one did this one yet)

Sheila & Felicia Masters - Feel Good Time by Pink

Rei Anasazi - Leave You Far Behind by Lunatic Calm (I kind of always pictured this song in a big dramatic fight between her and another speedster across a huge stretch of desert and jungle......but that's me)

Midas - Society by Eddie Vedder
http://www.youtube.com/watch?v=Cy6iwP9Ux3A

Zack Ryder - Guaranteed by Eddie Vedder
http://www.youtube.com/watch?v=IWgxntibBtE

Phantom - Guerrilla Radio by Rage Against the Machine
High Wire Escape Artist by Boysetsfire

Serapheal and Belial - My life by 12 Stones