One of my Bandcamp favorites is Pallbearer's 2010 Demo. This is flawless melancholic doom with an old school vibe, great guitar solos and killers vocals in the traditional Ozzy style. Here's a review from Lurker's Path.
The last song of the demo is a fantastic cover of the Billie Holiday song "Gloomy Sunday". Pallbearer even replaced the last verse with its I-was-only-dreaming-everything-is-ok lyrics with a soaring guitar solo. A Doommantia review (no longer online) called it "a great track but the weakest track out of the three tunes ... they are much better at sticking to their own material". I disagree, but listen to "Gloomy Sunday" (and the rest of the demo) below and judge for yourself.
Dearest the shadows I live with are numberless
Little white flowers will never awaken you
Not where the black coach of sorrow has taken you
Angels have no thought of ever returning you
Would they be angry if I thought of joining you?
Gloomy Sunday
Gloomy is Sunday, with shadows I spend it all
My heart and I have decided to end it all
Soon there'll be candles and prayers that are sad I know
Let them not weep let them know that I'm glad to go
Death is no dream for in death I'm caressing you
With the last breath of my soul I'll be blessing you
Gloomy Sunday