One of the most integral parts of my winter (and fall...and spring...and part of summer, now that I think about it) wardrobe is the perfect pair of opaque black tights. They have to be warm (because Pittsburgh is freezing), they have to be matte (but not too matte), they have to be thick enough that they don't get weird and spotty right above the knee (but not so thick they look like leggings.) And they have to last longer than one or two wearings.
Thank you, Sara Blakely, for answering all my nit-picky prayers.
Aside from all the smoothing goodness you'd expect out of Spanx, these are great because they're reversible. Two sides of color makes them extra opaque--almost like skater tights. They're super durable (I throw mine in the washing machine and still have the same pair I bought over two years ago).
I suggest you dash over to Nordstrom before their Anniversary Sale ends on August 3--this is pretty much the only time you can get these discounted. I buy a new pair every year.