One I Love by Coldplay, consigned to the realms of B-sides forever.
Also the album version of My Immortal by Evanescence. It is about to be released as a single, but the version I've heard on the radio is different. Guitars and drums kick in at the end, wheras the piano/vocals only version on Fallen is much better.
The singles market is a joke now anyway, for all I care they could be done away with altogether