Why just build a humaniod fighter robot? Check out the Bioloid Multi-bot Robot kit. Besides humanoids, you can build a dino, dog, spider and more.
The Bioloid Multi-bot kit has serial controlled servos that can be used in different configurations. With the multi-bot software the different robot creatures can be controlled.
Audio Cubes sells the Robotis Bioloid internationally for $899. Robotis is a Korean based company. Robot kits have been predominently from Japan so far.
More details about Robotis can be found on their site.