Update: I thought those 'emergency bivvy' bags were just a gimmick until a trip in the Gifford Pinchot
I bought a cheap one on a whim for like $8, thinking it was just more junk to fill my pack. It's basically a big orange plastic bag, right? Well, a sudden storm rolled in during a solo overnight near Mount Adams last fall, and my tent's rain fly tore on a branch. I was getting soaked and cold fast. Out of pure desperation, I crawled into that bivvy bag. I was fully expecting to just be a wet person in a plastic bag, but the thing actually worked. It trapped my body heat so well that I stayed warm enough to get through the night, even with damp clothes on. It was noisy and felt weird, but it did the job when my main gear failed. Has anyone else had a piece of cheap backup gear save them in a real pinch?