Ive had this little piece of gear in my day pack for at least a year now, and I don't know why Ive never done a post on it. This piece of gear happens to be the Sea to Summit Tarp-Poncho in ultra-sil. It's actually a pretty cool item to have in your kit. It's very small and pretty light weighing in at 12 ounces. Although I don't use it on backpacking trips, I do take it with me when I hike into remote native trout streams as an emergency shelter and, well, poncho. I figure that if I have to stay the night in the mountains (and I'm not backpacking of course) its because I have somehow gotten injured (If was lost I could just fallow the stream back). So with that said I most likely will not want to or be able to gather materials for a shelter. Also if I get caught in a rain storm, which I'm sure we all have at some time, I have a poncho to at least hike out in. I pair this up with a SOL Bivvy which is a high end space blanket and a small kit with a whistle, fire starting supplies, a few bandages, and some cord for a nice little survival kit (yes there is always a knife in my pocket or pack). I have added lengths of cord to the four corners for tie downs and have looped them on for easy removal for poncho mode or reconfiguring how I want to set it up. Its simple yet effective and good insurance to have if you ever have to stay the night in the woods. Heck I may even take it on a mild weather backpacking trip just to see what its like.
See you on the trail,
p.s. I should also note that I take a small aluminum water bottle as well which I can use to boil water. You can do the same for bring some other way to treat water.