Fire supplies (heat source and starter fuel)
Shelter materials (from simple space blanket, or nylon tarp/poncho up to bivy bag...just take something)
Water or filtration (life straws aren't great but they will do in a pinch, metal cup comes in handy too)
Cordage (paracord, twine, or vines )
Knife (sturdy enough to chop or dig)
If a person has these four things, survival for days is very possible in severe conditions or bad circumstances.
