If you were stuck on an island and could only bring five things with you, what would you bring? (And no, it cannot be a means of escape)
Only need 3: Knife, Flint, and fishing wire.
The knife for carving, rope making, hunting and shaping.
Flint for obvious reasons (fire)
and Fishing wire for stripping bark (Aid in rope making) fishing, and light item lifting (Stopping food from hitting the ground and whatnot.)
With those tools I can make a living and eventual escape if I dare so myself.
Off topic: Living in an island is like living in a seafood restaurant. There's food EVERYWHERE! Dig in the ground a bit? FOOD, climbing some trees? FOOD, even if there's a handful of vegetation, there's food around there as well. The obvious fish, small shark, and crabs, but if you've just entered that island there's periwinkle EVERYWHERE. FOOD!
Water's not going to be a problem either since there's many ways to store water.
The only problem is sanity. That's it.