I really like Anvil, but I love Raven. No-brainer.

Cianide - Gods of Death
Amebix - Arise
Uriah Heap - Sweet Freedom
Midnight - Satanic Royalty
Speedwolf - S/T

This is probably my favorite band of all time. I don't get the sludge comparison. I know nothing on that music, but it makes no sense to me. Medieval played very dirty metallic 50's rock n' roll in my opinion. All Knobs to the Right!