Assuming you're a normal person and therefore have a complicated, toxic relationship with your family such that you don't want your estate split evenly between your next of kin, a will with which to scorn each of them one last time.
Don't skip the paperwork for declaring your executor and/or a living will either - you don't want those presumedly slimy bastards making medical decisions for you while you're in a coma.
Assuming you're a normal person and therefore have a complicated, toxic relationship with your family such that you don't want your estate split evenly between your next of kin, a will with which to scorn each of them one last time.
Don't skip the paperwork for declaring your executor and/or a living will either - you don't want those presumedly slimy bastards making medical decisions for you while you're in a coma.