Prayer of St Francis by Sarah McLachlan. I'm not usually into Christian type things, but this prayer is just beautiful for anybody, I think. It's just something to strive to and whenever I'm feeling anxious or annoyed I turn it on.

I like
Song for a Winter's Night by Sarah as well, though my favourite is still Gordon Lightfoot's version, I do think her version was good.
Hallelujah by Jeff Buckley...Who Wants to Live Forever by Sarah Brightman. I love Queens version as well, but I love female vocals.
And this one is amazing:
Walkin' After Midnight sung by Fiona Apple. I think she actually does Patsy Cline justice on that one.
Those are just a few of the ones I like..

I'm always interested in covers because I like to hear different versions of songs.