I've been creeping toward ultralight for years, and for a weekend backpack this past weekend, by pack weight was 12 pounds! Wow, that is the lightest I've ever had. That didn't count food and water, but my alcohol fuel was in the pack. I think of this in terms of what I didn't take that I usually do take. For this trip I didn't take:
camp shoes
camp chair
extra clothes (that worked out fine)
big first aid kit (just band aides and moleskin, and advil)
fishing gear
extra camera battery (that worked out fine)
gloves
commercial bottles of "stuff" (I repackaged stuff like sunblock and bug juice into little bottles)
water filter (I took MSR purification tablets)
fishing gear (but at the last minute I through in a Tankara rod)
I really missed the camp shoes. I might add my crocs back to the pack. I really missed the camp chair, but I also really liked the light pack weight. That is a tough one for a 65 y.o. to do without.
Of the big gear I had:
Golite jam 50 pack, in which the top 10 inches were empty
Western Mountaineering Mega light bag
Tarp tent Squall II
Big Agnes sleeping pad
Caldera cone and stove, and Snow Peak Ti 900 pot
WM down coat
nylon long sleeve shirt
Golite merino wool hat
REI rain coat
my 2 oz cork handle knife
I could still lose some weight, like my wallet, and cell phone, and a one man tent instead of a 2 man. I also took my light Canon G12 camera and not my heavy Sony R1 camera.

