Water, Communication device, shelter(tarp/adequate clothing), food(non perishable snacks), knife, lighter, gun.... And all that other stuff. In that order!
First priority is supplies to keep yourself alive and get help. Keep them in something sealed that floats and somewhere that they will "pop up" if the boat suddenly disappears. Secondary is the stuff to salvage the boat. The specific items vary based on geography and weather, but the priorities don't change.
I have sunk a boat in the winter in 15' of water. I had all kinds of goodies and life preservers on board. The only thing that popped up was a cooler. Don't just worry about what you have on board. Pay attention to how you store it. They go down FAST!!!