Shelter, water, fire, food, first aid - these are the basic survival needs regardless of situation, so whatever tools best help you meet these needs is what you should have on hand.
Shelter - could be anything from a simple tarp or hammock setup right up to a multi-room tent - have some cordage on hand for binding, fastening, and lashing
Water - either bring your own or have a means of purifying water you collect, and make sure you have a vessel capable of boiling it in
Fire - have at least 3 different means of lighting a fire and the tools needed to process wood - axe, hatchet, knife, saw etc.
Food - no explanation needed, you'll need a means to prepare it
First aid - always have a decent kit on hand and know how to use it.
Comforts - this can be lighting, pastime items, music, camera etc.