I thought this would be an interesting topic, though I can maybe guess at what a few answers will be :P
What are your favorite pieces of clothing you've ever bought for hunting and why?
I'll start, I have a few. In order:
1. Aclima Woolnet Baselayers - YMMV but these have been a game changer for me. I no longer have to worry about getting sweated up on my way to a stand or blind, or worry about having to change clothes when I get there. Superior warmth, comfort, and drying properties IMO. The only baselayers I wear anymore, I get use out of them from the 60s down to the -20s.
2. Appalachian Gear Company All-Paca Hoodie - Light, warm, breathable, naturally silent and odor resistant. I love this thing and use it whenever I can, 50s down to -20s, outer layer or midlayer, stand or spot and stalk.
3. Dachstein Boiled wool sweater - Make no mistake, it's heavy, its not packable, and it certainly isn't cheap. That said I absolutely love this thing for stand hunting in late season. It's a heater, it's surprisingly good at blocking the wind and snow, and despite it's warmth it breathes exceptionally well. This sweater offers great flexibility, and is as quiet as any outer shell I've ever used, EVER. The collar is great, rising up tocover your neck in comfort and warmth. Another benefit is you can buy the Mil-Tec knock off for a third of the price and get 95% of the functionality.
4. Stone Glacier Grumman Down Vest - This thing packs down nicely, weighs pretty much nothing, and is sleek enough to wear under your shell without looking like the Michelin Man. Very happy with the amount of warmth it provides and it helps break the wind as well if you like to wear a wool layer over it like me.
5. Asbell Pathfinder + Mackinaw Cape - When it isn't cold enough for the Dachstein it's Asbell time. The Timber Ghost is the best camo I own, hands down. If you don't have a cape for your pathfinder or jacket, get one, you won't regret it. I have two capes, one hunter orange for rifle season and one Timber Ghost to match my pathfinder. I find myself wearing the cape over not just the pathfinder, but a lot of other stuff I wear as well. What's not to love? It's quiet, blends in with a wide variety of environments, breathes, and gives me the range of motion I need.
Honorable mentions - Woolpower 400 Ulfrotte vest, Swazi Cairnsman hooded sweater, Grey Wolf Woolens Boot Blankets.