I have a LL Bean Casco Bay windbreaker in my bag. It packs down small and light and the black is pretty stealthy looking. It is pretty waterproof, although I would want something a bit more in a monsoon. However it's perfect for my "bag". It's inexpensive, light and small and not being my primary rain jacket I can toss it in my bag and forget about it until it's really needed. Again if I were heading into a monsoon I would dress for it as I surely would have plenty of notice for a weather event like that. lol. For something to use in a emergency situation it excels!
http://www.llbean.com/llb/shop/68625...breaker-jacket