Anyone Western Mountaineering makes. Joking aside. Well maybe I'm not joking. I have the W.M. Hooded Aspen SMF now called the Sycamore. 25 degree - semi rectangular - 2 lb bag. Not the lightest but so versatile. If I'm dressed and prepared for 10 degrees with a little layering or a lot, ( if not sheltered ) I can still fit in my bag with room to spare and be toasty warm. Foot zip - two side zips- makes into a quilt total temperature control. Being comfortable from 6 to 60 degrees or at least survive a few nights at the lower temps without having to hike home because your freezing is a nice thing.

"Time is precious. Trek slower."