What type of will is completely handwritten by the testator?

A holographic will is one that is entirely handwritten by the testator, which gives it unique characteristics in the realm of estate planning. Typically, this type of will reflects the personal touch of the testator, as it is expressed in their own handwriting. This can often lend authenticity to the document, as the law often recognizes it as a valid form of testamentary intent, provided it meets certain legal requirements, which can vary by jurisdiction.

In contrast, other types of wills, such as a notarized will, involve formal procedures and are often typed and signed in the presence of a notary public. A codicil is an amendment or addition to an existing will and can be handwritten or typed but is not purely a standalone handwritten document. Lastly, a formal will is usually prepared by an attorney, follows specific legal formalities, and is often typewritten. Thus, the unique nature of a holographic will as being entirely handwritten distinguishes it clearly from these other types, making it the correct answer to the question.