Whereas the nut cracking is cool for the intelligence shown towards survival, the one that truly astounds me is intelligence for the sake of having fun. Crow skiing: https://www.youtube.com/watch?v=1WupH8oyrAo
A sense of fun and play seems to be the main way creatures have evolved to try new things and learn. I think this includes curiosity. It also seems common that it is young creatures that mostly engage in this behavior, and as we get older we get more serious and set in our ways.
