You're going to want wide-ish tires and possibly studded tires, for a start. You probably don't need fatbike tires just for commuting; think CX size. So you'll need a frame with clearance for those. I also highly recommend fenders, because at least where I live, winter commuting involves lots of sloppy, salty, brown slush in addition to the actual snow. So you'll want eyelets and clearance for those, too.
And you'll probably want a somewhat lower gear than you would in the summer, because you'll be grinding your way through snow wearing bulkier clothes in the wind, and if you're anything like me, your chain won't be running too smooth by the end of the season.
So you probably don't want super fancy pricey drivetrain components, either.

Other than that, it just depends on your preferences. I use the same bars for winter commuting as I do for road riding, because I like them. I commute on a Surly CrossCheck, which has room for fenders and reasonably wide tires, plus it has mounts for a rear rack, which I consider essential equipment for an around-town bike. It has short horizontal dropouts, which makes it work easily as a fixie. It has a durable powder coat and it's enough of a tank to survive life as a beater bike in New England. They are very popular around here for exactly that reason, although the CrossCheck is by no means the only frame that meets that description.