Metallica - Load: Along with its tween album (which I don't own) this is easily the best produced metal record I've ever heard. Seven years after the same producer would be ruining an album that had some good ideas for the same band (alongside an idiot who thought replacing his snare drum for a steel pot would be super). So, curiously, Bob Rock also gets my vote for the worst production of all time... and tbh his 2000's works are utter crap (check The Cult's Beyond Good And Evil).
Iron Maiden - Live After Death: Martin makes everything sound so clear here and yet gives it so much edge and attack. Not a fan of TNOTB, POM and Powerslave's production but Killers, SIT, Seventh Son alongside this monster of a live recording are absolutely flawless, each one on its own way.
Fear Factory - Obsolete: Why? Rhys Fulber... that's why! From the sampling to each single instrument to the immaculate mixing this thing is a "how it's done" template. Not my favorite record from the band but surely my favorite production.
Honorable Mentions: The Prodigy - The Fat Of The Land, SYL - Alien, Nine Inch Nails - The Downward Spiral & With Teeth, Control Denied - The Fragile Art Of Existence, Devin Townsend - Empath & Infinity, Fear Factory - Demanufacture & Digimortal, Sepultura - Chaos AD & Roots, Paradise Lost - One Second & Symbol Of Life, Pink Floyd: The Division Bell & Pulse, Slayer - Reign In Blood, Entombed - Wolverine Blues, Public Enemy - Apocalypse 91... , The Cult - Sonic Temple & The Cult, House Of Pain - Same As It Ever Was, RHCP - Blood Sugar Sex Magic among many others...