Lucifuge.
I love Danzig 1 but it still sounds like Samhain, almost Samhain's 5th album. Glenn was still writing primarily punk songs around D1 but the blues and hard rock influences were starting to show. D1 also still sounds like they were using the same production and mixing ideas from Samhain days. Not that that's a bad thing, but they just weren't "Danzig" yet.
Lucifuge was the album that defined Danzig as a completely seperate entity. Long way back from hell, Snakes of Christ, Tired of being alive, Killer Wolf, I'm the one, Her Black Wings, Devil's Plaything, 777, blood and tears,Girl, Pain in the world. Those songs are the complete birth of Danzig. Fat riffs, solid drums, chugging bass and the evil Elvis/satanic Jim Morrison vocals. You'd be hard pressed to find a better written and produced rock record.
Danzig 1 - Danzig 4 are 4 of the most important rock records recorded in the last 20 years.