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Outdoor Research Fraction Pullover
Everyone should own a PrimaLoft-filled jacket. Unlike delicate down, the synthetic insulation doesn't turn to mush when it gets wet. The Fraction's spare design and just-enough stuffing make it much more compressible than a midweight fleece yet warm enough for cold-weather camping or belaying. Bonus: The DWR-treated polyester shell fended off an hour of Wisconsin drizzle. $129; www.orgear.com

Mountain Hardwear Mastiff Pullover
Ignore the Sasquatch jokes: The Mastiff's beastly shag hides serious science. The fluffy material is Polartec's new Biomimicry fleece, which imitates animal fur. Longer “guard hairs” on the exterior create loft, while denser inner fibers trap warm air, giving the highly compressible Mastiff the best warmth-to-weight of any fleece I've worn. Stretchy side panels, thumb loops, and a cinchable neck round out the techy features. $140; www.mountainhardwear.com

Arc'teryx Sniper
Get a midlayer, jacket, and sidewalk cruiser with the three-in-one Sniper. During a ski trip in British Columbia, I was able to easily slide a shell over the fleece's fitted cut and smooth face. But Polartec's tightly woven Wind Pro fabric can go it alone, too: It beat back pine trees and stiff gusts in Colorado's Indian Peaks. And thanks to the subtle, sweaterlike herringbone weave, the Sniper can pass muster off the mountain as well. $150; www.arcteryx.com

Smartwool Synergy Zip T
After years of being faithful to natural fibers, SmartWool has hopped in the sack with synthetics, and it's been a fruitful affair. While ski-touring in the Tetons, I stayed warm and dry thanks to the Synergy's 100 percent merino liner, while the smooth nylon-and-poly face acted like a built-in wind shirt. The extra-tall collar is a blessing when things get nasty, and the welded chest pocket is placed high so you can access small essentials without undoing your pack's sternum strap. $150; www.smartwool.com