I'm amazed no one has mentioned EmmyLou Harris.
And...while we're mentioning voices, a shoutout to an underrated but incredibly versatile voice: Paul McCartney.
On a more general note...I think there's something about distinctive and unusual voices. Willy obviously comes to mind. You can never mis-identify him. But even Bob Dylan. While I know he's deteriorated in his dotage, there is something completely compelling about his singing during his better days. There are technically perfect/pure voices, and then there are the ones that are great because of how unique they are.