I either like big, strong, powerful voices, or soft, light but still strong voices
So:
Alicia Keys
alan
ayaka
Baek Ji Young
Chihiro Onitsuka
KOKIA
Beyonce
A-mei Chang
Adele
Also this group always has four or five of the prettiest voices ever. They've changed group members a couple of times and this is the most recent line-up:
And one more. I've only been watching Glee for a little while, by my god Chris Colfer's voice is just amazing. Almost every solo performance he gives is enough to leave me in tears. This one especially:
(on the show)
(live)