Up, up, and away in my beautiful Mars exploring balloon!
That's why I'd like to see something like a dirigible sent to Mars, which can fly over most anywhere under its own control, could touch down at interesting spots, drop off miniature stations, then take off for the next interesting spot.
Could it be delivered to Mars without the mess and fuss of having to actually land first? Could it be released at a certain point above the surface to start doing its work?