(Video Link) The RHex robot has six spinning legs and a bulldog determination. It can keep on going even after it gets flipped over. It can tackle rocks, fallen logs, and shallow water, and has the good sense to turn around in a narrow cave.
It's hard not to think of the pendulum-style walking leg movements as the ideal design concept for legs, because natural analogues provide the default setting for our imaginations. Same problem for early airplane designers who kept thinking of flapping wings.