The last option of the poll had me laughing pretty hard...
When Nasa announces something im more excited than a kid on Christmas morning.
Its like finding something you lost years ago times 1000.
My pure guess - traces of H2O
Water discowered on mars long time ago. Polar caps on mars contains a lot of water. It's not a sensation. But finding living microorganisms on mars will be a sensation. That would be exciting. Im waiting for this.