Whistle / Signaling device.... If it's not on the list, it should be. I often encourage newbies, or those unfamilliar with the area, to carry one. In this part of the world, you don't have to step too far off the trail to be lost or separated from a group. Two way radios aren't a bad idea for a group either, with one at the front and one at the back to keep everyone accounted for.
Flashlight should go on every trip, at this time of year especially. It doesn't take much of a delay to get caught in the dark.
^^ Livin' in the 3rd dimension - Go Vertical !!