CMU has something for you. It's a lower leg only exoskeleton that's unpowered and reduces the amount of energy used to walk by about 7%.
That's the equivalent of being about ten pounds lighter - making this useful for anyone who has to work on their feet all day (the designers plan on marketing it to nurses and similar). It may also be good for disabled people with conditions that make them tire easily.
(For that matter, I wouldn't mind one for conventions...)