6. Boston Dynamics BigDog
This rough-terrain robot can walk, climb, run, and looks f*cking terrifying doing it. At roughly three feet long and 2.5 feet tall, BigDog's on-board computer controls locomotion, processes sensors and handles communications with the user and can run up to four mph.
Let's hope these things are never used for war, because just imagine that thing running toward you. Horrifying.