Bump because I've really been getting into this band over the last weeks (months probably).
So far I only know The Fragile, The Downward Spiral and With Teeth, but I love them all, and I am planning on checking the rest out, I just love taking it slowly so that I can appreciate everything.
I would probably rank the albums in the order I mentioned them, The Fragile is my favorite and it's hard for me to pick a favorite disc on it since both are so good. I don't get the hate for Disc 2 at all, it has "Into the Void", "Where is Everybody?" and "Please" (one of my favorites) just to name three really good songs, and I think the rest is fantastic as well. The Downward Spiral and With Teeth are pretty close right now. The first is such a journey and I love it, the latter is more of a "catchy, more straightforward songs" which is fine as well. "The Hand That Feeds" and "Every Day is Exactly the Same" are two of my favorite NiN songs so far.
So to keep it short: awesome band.