I think I have talked about this before, but from the medical side, I wish everyone would have the following:
1. Living will or advance directive
2. POLST form if you don't want to have the aid unit/medic one resuscitate you at home
3. Durable power of attorney for health care
3. Durable power of attorney for financial matters
5. Your wishes in terms of funeral, body disposition, etc.
It makes it really difficult for us in the hospital when Grandma is dying, the family members don't agree on treatment, and some people think that Grandma would have wanted to just die, but of course Grandma never got around to writing this down or completing a form.
My other pet peeve is the people who download a power of attorney form from the Internet, fill it out, and then present it when Grandma is in the hospital. I have to tell them that they downloaded the wrong form, and the power of attorney they have is for financial matters only, and it gives them no authority over healthcare.