Gonna be one hell of a weird combination... but here's my band:

Guitar: Tool's Guitarist
Bass: Modest Mouse's Bass player
Lead Vocals: Maynard (need more be said? Tool and APC rock...)
Backup Vocals: Gwen Stefani/Sublime
Drummer: Tool's Drummer

As you can see... i'm a pretty big Tool fan... ::shrugs:: but this would be my dream band...