Essential
-water
-food (lunch and/or snack)
-raingear (jacket and pants)
-extra sweater or fleece
-map
-large orange garbage bag (can be used as emergency shelter or to signal emergency aircraft)

Recommended
-first aid kit (band-aids, alcohol wipes, 2 bandanas or triangular bandages, tweezers)
-compass
-knife
-flashlight
-solid tread shoes (hiking shoes or boots, not running shoes)
-lighter or waterproof matches
-sunglasses