Here is what I think they should sing:

Bo Bice: "Cowboy"- Kid Rock, "Disco Inferno"- 50 Cent
Constantine Maroulis: "Zorba the Greek", "Screams of the undead"- Demon Hunter
Mario Vasquez: "I am sissy/Let us be gay"-?, "Hats off"- Alabama
Anthony Fedorov: "I watched my dream crumble like Clay."
Scott Savol: "Ugly"- Bubba Sparxxx, "Fat Man"- Jethro Tull, "Psycho Nightmare."- Daniel Johnson
Mikalah Gordon: "Born Annoying"- Helmet, "I won't shut up."- Charlie Allen?
Amanda Avila: "Simon's Kiss"- Lisa Coppola
Janay Castine: "Deer in the headlights"- Kelly Burns.