I've probably been here before, but it changes a lot, so..
Tom Meighan and Sergio Pizzorno of Kasabian, Thom Yorke of Radiohead, Brett Anderson of Suede and Matthew Bellamy of Muse are some of my faves, but if I only could choose one, then it would be Jonas Bjerre of Mew. He has such an angelic voice <3
Enya and Jarvis Cocker of Pulp are pretty awesome too
Natsuki Ogoda from Passepied! I know that for some [if not a majority of] people, her voice may take some time to get used to; but I personally think that her voice sounds cute and unique! Kaikazensen, Tow-Ryang-Say, and China Town are my favorite songs from them, and I really think her vocals add to it!