Alcohol Stove - small, lightweight, and virtually unbreakable. Fuel for this stove can be bought at most gas stations in the form of HEET, a cold-weather gasoline additive that is mostly methyl alcohol. Isopropyl alcohol and denatured ethanol also work.
The Sleeve - a soft scrap from an alpaca sweater. A last minute addition to Kevin's gear, this tight-woven piece of cloth became a balaclava for cold-weather protection.
Sunglasses - sun, snow, blowing sand, and wind protection. If you forget yours, just keep your eyes searching the shoulder and you may soon find a free pair, as Kevin did.
Silk Liners - sewn from old garments (found at Goodwill), silk adds lots of warmth without a lot of weight or bulk. Along with ~35 degree F down bags, mylar "emergency" blankets, tyvek bivy sacks, and closed-cell foam ground mats, hand-sewn silk liners played a big role in keeping our bedrolls both warm and packable.
Thin gloves - despite daytime temperatures below freezing, these minimalist gloves performed better than their technical cousins could have. Wind protection plus breathability keeps hands comfortable and dexterous while exercising in cold weather.