This should be easy, and yet… it’s really not. I was going to say my kindle, but electricity would be an issue soooo not useful at all. I guess I’d be practical and go with a knife, a watch, a pot… and pen and paper. With a knife I can get food, shelter and protect myself, a watch I can make fire with the sun, use the hands for a compass.. or a needle to sew with, a pot to cook with and clean water. With the pen and paper I can entertain myself for a while… drawing and writing.
What more could you ask for? 😛