Don't care that much about lyrics, and I prefer vocals to be subordinate to the music. To that extent, the best use of vocals for me are those that do something other than simply sing (not that singing is necessarily simple).

E.g. the melodic refrain that opens Curve's Coast Is Clear which you might pick to be guitar, but is actually Toni Halliday's humming put through a butt-load of effects:

http://www.youtube.com/watch?v=zk2l5ClkOMY

In a different way, I love Kaito for the way the "singing" seems much more about simply adding texture and noise to the song than relating lyrics, like in the "chorus" of "Should I":

http://www.youtube.com/watch?v=iQsjK96ptaA

More obvious examples are Bjork's Medulla, and the practice of beatboxing.

Anyway, hit me up with your favourite uses of vocals for non-singing/rapping purposes.