I have a special love for female vocals, so I pretty much enjoy them ALL. A good female vocal can even transcend my overall musical preferences. That said, I make an exception for Lykke Li. I don't know why, but her voice (or style of singing, perhaps) grates my nerves something fierce.
I'm much like Orangey in my feelings about female vocals, so it's pretty hard to list. I can only throw out a few that come to mind knowing there are countless others.
It is worth saying that Annie Lennox will probably endure as my favorite. There are quite a number of songs she's done that I don't really even like, but I always love her voice one way or the other.
Lately I've been listening to a lot to Annie Clark (St. Vincent). She's pretty damn good.
I also have to give a special mention to one I'm conflicted about, and that's Mette Lindberg from The Asteroids Galaxy Tour. She sounds like she's 10, has a Danish accent and sort of an impediment, and kind of screws around with her voice a lot. It makes perfect sense to me that many people find her singing infuriatingly annoying, but for some reason I love it.
Go to sleep, iguana.
INTP. Type 1>6>5. sx/sp. Live and let live will just amount to might makes right