This may be the smallest/lightest piece of gear that has the greatest potential to save your life in a not so uncommon emergency... getting stuck in the wilderness overnight without shelter. If this situation occurs in mild conditions, this bivvy will keep you from mild hypothermia. However, if you're backcountry mountaineering and SOL stuck in a surprise storm this little fella can mean the difference between surviving and not.
Also, I think it's superior to the emergency blanket because your body is sealed from the elements, instead of having to worry about gaps.

These sacks are really excellent, I own multiple sizes to keep my gear organized in my pack (especially useful for longer excursions), the different colors definitely help for this use. Also, being waterproof, I don't have to worry about moisture or humidity getting into my gear if it rains/snows. I have an XS that perfectly fits my backpacking electronics and backup batteries. The only thing that takes a bit of time is figuring out how to fully compress these guys while you're sealing them up. But it'll only take you about 5 min to figure out a technique that works (I compress it against my chest while rolling it shut).

This beanie is super warm and has a neat little stash pocket for your stuff.

If you've got big feet you know how hard it is to find a board wide enough in order to prevent toe-drag! Then, once you got the super-wide board you realize that it's a real pain in the butt to make edge-to-edge transitions. Well, I got the PLS supers and found that not only can I slightly reduce the width of the boards I ride (now I'm in the 25cm range instead of 26cm+), but they also allow more leverage for edge transitions since your feet are further from the ground (or fulcrum point for that matter). They take a little getting used to though (because it's harder to really "feel" the board), so take it easy after you first dial these puppies in.