Carhartt's Arctic Extreme Bibs. Bibs do a way better job when the wind chill is -40 (like it is today). A good coat that's made out of something tough (like Carhartt), a hood is really nice to have. With the bibs you don't have to have a super long coat so sitting in the plane with it on is a lot easier.

I've used polypropylene long underwear for 20+ years and like em. Will keep you from freezing in your own perspiration.

A good face mask is required.
A REAL Alaska hat...mine is beaver fur and with a face mask I could ride my snowmachine out to the airport and be fine. Another plus is if you're flying a piston single you can put your hat on the dash and keep a little spot of windshield from frosting over so you can see to land.

Mechanix gloves or soft leather gloves for slinging freight and mail. Warmest ones you can get for winter ops. I also carry a pair of polypropylene glove liners that weigh nothing and are great inside your heavy stuff or alone on "warm" days.

I don't wear bunny boots because I have a size 14 foot. Bunny boots biggest advantage is if they get wet they will warm up again. I've always wore Sorel pack boots and they work fine, just don't get the felt liners soaked. Have an extra pair of liners back at the pilot house and rotate 'em so they stay dry.

Summer time if you don't have a mosquito head net in your flight bag your just plain stupid. You've never seen a mosquito until you get to western Alaska...

A 100% waterproof jacket and I like soft shell hiking pants for wetter weather as they shed water well and dry quickly, plus comfortable and easy to move around in.

Many years ago a friend told me an old Norwegian saying, "there's no such thing as bad weather, just bad clothing."

Just my 2 cents