In my business this is considered forum shopping, but if you have any real money at all, defined as more than $2 million dollars, please do not die in Washington State. An aggressive tax scheme begins at that point.
Some other bad places for your family but good for the tax collector are Oregon, Minnesota according to the anecdotal evidence which has washed up on the shores of Puget Sound and found its way to my office.
On the other hand if you are worried not about taxes but instead just want to die easy and see your family have your worldly goods sooner than later, avoid California and Florida.
This assumes you can plan your own death. How bourgeois.