This 2007 Gear of the Year summer bag is super-soft and impressively warm for the low weight. Plus it lets you chill without being chilly: It unzips to the hips on both sides, freeing your arms for reading or cooking while keeping the rest of you snug. A face gasket and trim hood seal in heat. 32°F, 2.2 lbs; mountainhardwear.com
Bonus: Stuffs down to the size of a football.
Bummer: The zips don't provide adequate venting in the warmest weather.