I think reusable orbital entry vehicles
The shuttle was very impressive in that they made it work, but in accomplishing the goal of low cost access to space ? Not so much.
Mars landers, and the half a dozen other probes scattered on missions throughout the solar system might be something to brag about
Viking was 1976, nice thing for the Bi-Centenial if your young and Bi Curious you might want to google that. But it's nearly 40 years gone.
What they haven't done is make space more accessible, arguably Arianespace. Orbital Sciences and Space-X have done considerably more in moving humanity towards being a spacefaring species.