It depends who I'm drawing!
For Heart Hex:
If it's a Lee-heavy scene, I tend to go more with The Dresden Dolls, Agent Fresco, I Monster, and Aeon Fux/Guayaba. Anything that feels eerie and talks a lot about lost love or regret. If it's Teo, I tend to listen to Porter, Zoe, Motion City Soundtrack or Bayside. Lots of Mexican rock and pop punk. Rosier... I tend to listen to soundtracks or musicals. He's very theatrical and I need to get pumped up. E Nomine and the Tanz Der Vampire soundtracks are favorites.
And if I'm working on Future Girl? I play a lot of upbeat, female-fronted bands, like Fight Like Apes, Girl in a Coma, and Shiny Toy Guns, or Amanda Palmer.