Non-winter: a MontBell Ultralight Stretch Down Hugger rated to 32°F or a GoLite Ultra Quilt inside of an ultralight bivy. Use a 2/3 length Thermarest ultralight pad underneath. Total weight just under 2 pounds for the first setup, 2.5 for the second.

Winter: a Western Mountaineering Antelope (-5°F) or Valandre La Fayette (same rating, though I pushed it to -14°F and was still perfectly warm inside a tent), over an Insulmat insultated lightweight inflatable pad topped by 1/4" blue closed cell foam. Total weight under four pounds for everything.