Tie in here to an earlier clothing post. Ponchos are the first thought for a kit;light, easily donned and multi functional. A poncho WITH liner is an expedient shelter and groundcloth. I have several precut lengths of paracord and large bridge nails ( cut short) to expedite this assembly. Without the liner however, most contemporary ponchos become flapping invitations to rain. They are to light in ripstop nylon and poly. A dedicated rainsuit ( sou'wester hat, jacket and bib pants) is the best, but slower to don in a downpour and harder to vent. Lastly are the full length coats, such as the cowboy slicker and Australian oilskins. If you have long arms, the Aussie coats will feel short and require periodic redressing. They are truly weatherproof! Both will also convince a pack animal you are a boogieman without previous training!