"Ghost Bitch" hands down.
Other Godhead: "Brother James", "Making the Nature Scene", "Shadow of a Doubt", "Brave Men Run", "Early American", "I Wanna Be Your Dog", "Shaking Hell", "Star Power", "I Dreamed I Dream"
I like some of her later vocals, and love some of the songs, but must say, it's her early vocal tracks that I absolutely love. This is not how I feel about Sonic Youth as a whole, but I can't think of a song after Evol I'd put her vocals in league with any of those. Which is not to say I don't love "Drunken Butterfly" or "Nevermind", it's just a different ballgame.