A rain poncho is the most useful square of fabric you can carry. Ours is 210T rip-stop polyester with a polyurethane coating rated to 3000mm, cut to the full military pattern at 62" x 82". That's long enough to cover you and a loaded pack. Eight grommets give you tie-out points, so it rigs just as easily into an A-frame shelter, a lean-to, a ground tarp, or a hammock rain cover, and sixteen snaps let you close the sides.
Nine camo patterns, 18 oz, packs down to 6" x 8" x 3". Tie a USGI Poncho Liner into the grommets and you've got a two-piece system that handles rain and cold together.
