+1 on the headlamp. Petzl e+Lite is nice, compact, and light.
Also some T.P. and/or Kleenex, baby wipes, Advil, Immodium, Pepto, eating utensils or sporks, Leatherman or similar multi-tool, SAK, duct tape, zip ties, basic compass, flashlight, spare batteries, camera, first aid kit, emergency ponchos, trash bags, bottles of water, snacks, medium-sized cooler.
And oh yeah... most importantly... road maps!