One thing missing from Curiosity, that seems an obvious oversight since it’s included on every mobile computer now, is a MICROPHONE! It would be more of a novelty than anything, which is why it was left out I’m sure, but we apparently have not heard actual recordings from the surface of another planet before.
There have been attempts before to put a mic on Mars, but none have returned data. We’ve got synthesized sound only.
Saskboy's Abandoned Stuff 