Legal Representation: You have the right to represent yourself in a legal proceeding, but you cannot assign that right to anyone that you choose, only to certain approved individuals.
Vote: You can vote, and you cannot assign that right to another.
Jail Sentence: You can (indeed must) serve a jail sentence or be executed for a capital crime yourself, but you cannot allow another person to do that on your behalf.
Military Draft: When we had the draft (most recently), you could not authorize another person to serve in your stead.
Marriage: You can marry your neighbor's sister (if she is not related to you), but you cannot transfer that right to your neighbor (who is the brother of the intended bride).
These are different things from committing suicide, but it's not clear exactly what concept of exclusive sovereignty you're getting at.