I'm not exactly a top level producer or engineer, but these 'heavy' albums appeal to me for their production, all for different reasons.
Killswitch Engage - The End of Heartache
Impossibly polished yet still bone crushingly heavy, this album is super slick but doesn't have an overly processed or sterile sound but instead is very warm and sounds huge. The bands guitarist Adam Dutkiewicz produced this and has done a few other albums as well, he's amazing.
Meshuggah - Chaosphere
I could've picked any of the Meshuggah albums but this one does it for me. It's heavy from start to finish but even with guitars tuned so low, and the focus on guitar/drum/bass heavy rythms, the definition with each instrument is still great. And the vocals just jump out like they're going to rip you're head off.
Lamb Of God - As the Palaces Burn
Produced by Devin Townsend, this is a dirty and raw sounding album, but seems to suit the band perfectly. Only criticism is maybe the vocals are lacking a little bit of presence.
Machine Head - Burn My Eyes
I think someone said earlier about The More Things Change being a great one, but this is better IMO. The guitars are massive and incredibly savage, and the drums are pounding, overall a cleaner and more precise sound than TMTC. Has dated impressively well for a metal album and still sounds relevant today (even more impressive considering it was the bands first release).