1.Water Purification and some sort of bottle:I have had good luck with the chorine dioxide tablets for water purification.
2. Knife and usually a multi-tool as well
3. Some sort of flashlight or headlamp
4. raingear
5. firestarter
6. first aid kit
7. hat
8. paracord or something similar
I have used canvas packs and I always line them with Trash Compactor bags (more durable then regular trash bags) to help waterproof them. Where I pack things depends on who I am going with. If the wife is carrying the baby then She gets most of the light stuff and I end up with the heavy stuff. 🙂