This should bring out the UL gram weenies.
Besides lopping off wt by whittling down a toothbrush or cutting off clothing tags or shortening pack straps, I've:
1) weighed different plastic baggies to determine which one to go with - uh, the lightest wt ones of course.
2) spent close to $40 on a EVent stuff sack to save 1/3 of 1 oz compared to going with a 1/3 of 1 oz heavier one I already owned costing about $10 that was perfectly usable and WP too.
3) since I take a host of various supplements both on and off trail I've purchased supplements for on trail use based on their volume and wt rather than opting for the same supplements BUT IN OH SO SLIGHTLY of a heavier and more volumous version.