This one is pretty easy I'd bring a hatchet, for the simple fact it has multiple uses. It can be used as a means of defense, cut wood cut fish hunt for food smash etc, a bundle of uses. Then I would also bring a metal canteen for water, that also includes boiling it to make it drinkable. A lighter, just in case i can't find wood or stones. But in all honesty all I would need is a hatchet, most of the stuff i could find on the island unless it was barren. The other two are more of a backup plan, to fall back on.