First issue of Wired in 2006 published a list of The 50 Best Robots Ever. Unfortunately, my favorite robot, Johnny-5, was not on the list, even though the list includes many movie robots. I found it on The Ten Best Movie Robots list.
Out of those robots that were on the list, my favorite is Genghis, a six-legged walking robot created by Rodney Brooks and his team and covered with much detail in Brooks's book Flesh and Machines. Its unique (for its time) feature was that it was based on the subsumption architecture (described in more detail in How to build complete creatures), which provides an incremental method for building robot control systems that link perception to action. This control system is implemented as a set of layers, with each layer progressively implementing more and more complex behavior; robot's macro behavior (following people) arises from many independent micro behaviors (moving legs, balance control, steering, and the like). Conflict resolution happens at the motor command level rather than at the sensor or perception level resulting in coherent, smooth, and, as Brooks calls it in his book, "lifelike" behavior. However, contrary to what the Wired article says, the robot doesn't learn; this behavior is "innate" and doesn't change with time.