Flint & Steel (for fire)
Hunting Weapon (for food and protection) You never know when pirates might attack
Medicinal Kit and a great one. ( Like Dr.house inside)
Tool Kit (Hammer ..Saws..Rope..Nails...Screws..Etc)
Since you said desert Island I'm assuming that there's no internet or contact with the outside world so....
A Beautiful Woman.... If I can't have that then I better have an inexhaustable supply of alcohol!