The most important thing is proper cloths and shoes or boots for where your going, after that:

1. full water bottle
2. good multitool
3. metal cup/small pot
4. blast match, or some sort of striker based fire system
5. water purification tabs or filter
6. map/compass
7. headlamp

if you think you might be stuck out there a few days

100ft paracord, a tarp of some kind, blanket of some kind or an emergency blanket to save space, a good camp knife, some food, and a small med kit. that should keep you alive for at least a few days