Water (amount appropriate for outing/weather)
Lunch and extra food
Clothing appropriate for outing/weather
Rain gear
Map and compass
Headlamp or flashlight (extra batteries)
Whistle
Waterproof emergency blanket
First-aid kit
Hiking poles (if you use them)
Work gloves (for work hikes)
Bright clothing (in hunting season)
Snowshoes/skis (in winter)