2-liter water bottle (see our Dehydration & Heat Illness page)
High-energy snacks such as nuts, fresh or dried fruit, raw vegetables, etc.)
First aid kit (see our First Aid and A to Z pages for blister & hiking first aid tips)
Waterproof jacket, extra layer of clothing, & extra pair of socks
Map & compass
Matches
Glasses/contacts/sunglasses
Journal/pens/pencils
Camera/film/binoculars
Wallet/ID/money
Lip balm with sunscreen
Bug spray with DEET (see our Insects and West Nile Virus pages)
Sunscreen
Pocket knife or multi-purpose tool
Whistle, mirror, or other communications devices - remember that cell phones usually do NOT have a signal in remote areas
Tissue/toilet paper/sealing plastic bags (to carry out personal waste)
Hand sanitizer/portable hand wash towelettes