Portable Phone Charger: With no ship and no power, your phone will need some juice. A powered up portable charger in a waterproof container is a must.
Medical Sea Pack: In case you get injured or must survive days away from a doctor, you'll want to pick up a mini medical kit. Again, one that is built for ocean survival.
Watermaker: While these things aren't cheap, they will save you from dehydration by filtering out almost all of the salt in your drinking water.
Peter Dinklage is vegetarian. All the meat he eats on the show isn't real.
Knife: Generally blades under four inches are allowed on board, but check before you go. The smart play would be to get a Swiss Army Knife for all the extra gadgets.
This poster must have made the REAL Leatherface reveal even more horrifying.