People always upload 8-Bit covers to YouTube but rarely are they Metal covers.
Check out these NES-ified Death Metal (and other) tracks. Check out the other videos if you're into this type of thing.
Bolt Thrower - When Cannons Fade https://www.youtube.com/watch?v=XBhV8ayvhYc
Necrophagist - Fermented Offal Discharge https://www.youtube.com/watch?v=NImI7SRX3l4
Asphyx - Last One on Earth https://www.youtube.com/watch?v=DqYuOyxkJHo
Pestilence - Land of Tears https://www.youtube.com/watch?v=zJTNPMax4i8
Venom - Warhead https://www.youtube.com/watch?v=OQHNve8LS1w
Obituary - Slowly We Rot https://www.youtube.com/watch?v=yjFggzsJsdM
Death - Pull the Plug https://www.youtube.com/watch?v=kYA3XKe9a_A
Black Sabbath - Children of the Grave https://www.youtube.com/watch?v=OP8n7nLwWj8