Camp Stool . I have a small, extremely light folding stool that nests down into my main pack bag. Having a good place to sit in camp becomes more important as you get older and your aching joints cry out for . . . Stuff Sacks . I've been obsessively collecting an assortment of draw-string stuff sacks over the years.
Stuff sacks get to be close to an essential with an internal frame pack.
Group Gear . The key here is knowing what's really group gear. Most experienced backpackers have at least one of each of the following items and, in a masochistic expression of egotism, want to bring their gizmo. This usually ends up with having too many of the following items on the trail. If no later than the final pack-up before leaving the trailhead, I recommend a group going over this list and weeding out unnecessary duplications and then redistributing weight.