The ScotteVest Tactical System V 5.0 is the most innovative piece of EDC gear I ever had. It's a nesting combination of 2 vests with detachable sleeves, which one can accommodate to any kind of weather (0-100F), and which allow to carry a lot of [survival] items (small and large) concealed in it.

They don't make it anymore, but it's a combination of Revolution and Fleece 5.0, zippering one in another.