My most valuable secret in my mind would be my Heroic Self.
I always hope that I somehow have super power so that I can save this world from any catastrophe.
This is why I love to watch Heroic movies.
This definitely cannot be stolen because if it was stolen, the world will lose another Hero in the making.
And if I lose my Heroic Self, my Villain Self might take over and the world will have to deal with yet another Super Villain.
But the most important thing is that if it was stolen then I might lose my self and I will never be me again. LOL!!!