What do you have already? I assume you've played out your tool, disturbed, slipknot, system of a down....If you are feeling emo I suggest some goth metal from HIM or Marilyn Manson. Can't go wrong with Static-X (Played 8 encores at masquerade a couple years ago). Blood Simple is good...leans towards the metal spectrum. Atlanta boys, Sevendust can blow it out live. I've seen them all and they can all represent. Hardcore is gay; however, I will always have a place in my heart for ICP (I know they are horrorcore, not hardcore).