Algodoo

Little's walker: http://www.algodoo.com/algobox/details.php?id=251762

Unfortunately, I don't have the original walker, but I did take a picture of it before deleting it. This is my best reconstruction of the original walker, the spring length and motor rpm may be incorrect.
Mine wins for simplicity, being just 8 objects in total, and having built it in about 2 minutes. The fact that it keeps pace with Little's overengineered walker says a lot about Keeping It Simple Stupid. Lol.