A bit surprised 6VCR isn't mentioned yet (though they are so much amazing pixel artists out there anyway, including all those that are already in this thread that i won't repeat)
But yeah, 6VCR. I can't put in words how beautifull her work is. It's incredible.
https://twitter.com/sixveeceear

Tommi Laurila does some wonders too, https://twitter.com/PxTommi