Don't know if either of these have been mentioned..
Randy Meisner and Timothy B Schmit, both of the Eagles. Very tasteful playing while still singing harmonies and lead vocals. In particular, listen to TBS' fretless meanderings on New York Minute from the Hell freezes over vid. superb playing.
Also, I was watching Sympathy for the devil last night. hadn't realised Keef played the bass on that track letting Bill W do percussiony things. His playing isn't too shabby and I'm wondering what else he took over the bass part for.