What is it?

While on vacation, one year, grandpa took us to Hollywood. And I got to see the pictures of many famous movie stars. Arnold Swartznegger in "The Terminator", Sally Field as "The Flying nun", Michael Fox in "Back to the Future" and as I remembered them I asked my grandfather this question;

“Grandpa, what is it that the Pope has but it has not been used for awhile now,
You have one but grandma uses it and nuns do not need one,
I have one but my sister will never get it from me,
Governor Schwarzenegger has a very large one and Michael J. Fox has a very small one?”

Grandpa just looked down at me, his eyes a-twinkling, while grandma just looked away as she blushed and muttered under her breath, “boys, what will they come up with next?"