IF your goal is long term survival everything that has been mentioned and then some..... If you need assistance/rescue just three items. My son is a DPS Air Rescue helicopter pilot and his take was Personal Locator Beacon, cell phone, plenty of light sources. Good PLB's are capable of transmitting, who you are, where you are, medical history etc. Couple hundred bucks. Signal mirror can be seen from the air for miles. At night even the light from a cell phone can be seen from a great distance if the rescue crew is using NVG's. For ground rescue Kernel Crittenden is right on with the whistle. Make sure someone knows where you're going, when to expect your return and who to alert if you don't. Water is MUCH MORE important than food...you can go days without eating, not so water. Can't imagine a REAL long term survival situation but I guess all good Boy Scouts should be prepared.