Bit late to this, but just noting for future readers that I just made one at age 25 in a batch along with power of attorney documents and life support / living will directions after seeing how useful power of attorney documents were with a family member's medical treatment.
Link
One of us is no more.
He deserves a eulogy more eloquent than what I am capable of writing. Here's Cory Doctorow's, one of his long time friends.
It's a sad world in which you are being arrested and grand jury'd for downloading scientific journals and papers with the intent to share them.