I want to ride the Mars Rover Curiosity. Sure, at a maximum of 90 meters (300 feet) per hour it would be a glacial ride, but the bloody thing is going to Mars. Where have I been lately? To the dog park two blocks from my house, that's where. Plus, there's no dog poop on Mars.
But besides going to Mars, Curiosity will do science like never before. It will probably give us a definitive answer to a question that has been haunting the sleep of scientists, sci-fi writers and amazing singers with a permanently dilated pupil for decades: Is there life on Mars? Curiosity will also study the planet's geology in incredible depth, thanks to new instrumentation that would be able to study the core of rocks. And, equipped with the highest resolution cameras ever deployed in the Red Planet, it will take amazing high definition planet porn (sadly, the 3D camera championed by James Cameron was canned).