The newer Cooper STT Pro's are apparently really great in snow, also incredible off road. I have them but haven't been in ice/snow with them yet, but Eddie swears by them.
I should clarify that my reviews of the Cooper STT Pros in the snow is based on a comparison of all the "mud terrain" tires I've run in the past. This is NOT to say that they perform better than a good "all terrain" tire.
For snow and ice, it's really hard to beat a set of Duratracs.