Well, so far, something has been terribly amiss from the listed items. If you only get to take six items, then you obviously don't want to stay on the island forever. You almost certainly have to make one of the items a PLB, or short that, a signal mirror.

The other five should spread through the standard necessities of survival: water, shelter, fire, food, tools, etc. Keep in mind that some categories can be improvised from others (i.e., build a shelter using tools).