"Don't leave home without the Verto!" has become a joke in our house as it seems everytime we don't bring our Verto Jacket (made by The North Face) we wish we had. It is an ultralight, ultra-compressible shell that just gives you that little extra protection from the elements to get you through the day. And based on it's size, it packs down to a little bigger than a CLIF bar, it is pretty silly that we wouldn't always bring it. I am not sure if they are still making this jacket as it is not on their website, but you can still find it online at sites such as http://mountain-op.com.
We also love the Verto26 pack which doubles as a sleeping bag stuff sack and summit pack, working double duty to save weight.