I ran Pirelli Snowsports on my MSP for years, and they were excellent tires. The specific 'model' I had isn't made anymore, but I believe their Winter 210 Sottozero is the current equivalent. They're on the pricey side, though -- listed on Tire Rack for $133 each.
http://www.tirerack.com/tires/tires....omCompare1=yes
At the moment, I have Dunlop Winter Sport M3 tires on my G35 Coupe .. Got to try 'em out in the snow for the first time this morning. They did great. I tried to engage a slip going downhill a few times, and between the traction control and the tires, I couldn't get the car to break loose. The Dunlops are listed on Tire Rack for $105 each at the moment.
http://www.tirerack.com/tires/tires....omCompare1=yes