I'm not a fan of guest vocals, but Sparklehorse hit the button with Dog Door and Tom Waits on It's A Wonderful Life. Jon Spencer guesting on Boss Hog's debut also worked well, but what about when it doesn't work? Richard Hawley on Elbow's Seldom Seen Kid was one of the deal breakers for me on that album (and I like them separately).

What guest vocals on standard (by which I mean generally non collaborative) albums do you like and which do you not (and why)?