There's nothing like a great diva collaboration. Every time we see two top-notch chanteuses join forces, it feels like something special is happening. Miley Cyrus and Madonna mark the latest combination to get us in the girl-power zone. Their duet on Cyrus' episode of "MTV Unplugged" recalls a slew of performances that have spotlighted the pipes of pop's greatest divas. Join us in jamming to these multi-octave gems. No man can do it better.