HRP-2 is the final robotic platform for the Humanoid Robotics Project headed by the Manufacturing Science and Technology Center (MSTC), which is sponsored by the Ministry of Economy, Trade and Industry (METI) through New Energy and Industrial Technology Development Organization (NEDO).

The total robotic system was designed and integrated by Kawada Industries, Inc. together with the Humanoid Research Group of National Institute of Advanced Industrial Science and Technology (AIST). Yaskawa Electric Corporation provided the initial concept design for the arms and AIST 3D Vision Research Group and the Shimizu Corporation provided the vision system.

HRP-2’s height is 154 cm and its mass is 58 kg, including batteries. It has 30 degrees of freedom (DOF) including two DOF for its hip. The cantilevered crotch joint allows for walking in a confined area. Its highly compact electrical system packaging allows it to forgo the commonly used "backpack" used on other humanoid robots.
(From Kawada)

Now, take a look at the Robonova-1 robot performing an assortment of martial arts moves.

The stable ROBONOVA-I can walk, run, do flips, cartwheels, dance moves and once programmed, is ready to compete in any Robo One Class "J" competition. Available two ways, as a kit, so you can enjoy building your robot yourself, or as a pre-assembled, "RTW", "ready to walk" instant gratification robot.

This fully articulating, 12" high, mechanical man is controlled with 16 powerful HSR-8498HB digital servos built specifically for the ROBONOVA-I by Hitec. Powering the ROBONOVA-I is a 5 cell, environmentally friendly NiMH rechargeable battery that delivers around 1 hour of operational time. Other battery options can include 7.4 volt 2 cell Lithium Polymer battery.
(From Lynxmotion)

The name of 'HUBO' was selected through self public subscription. Appearances design of HUBO took the help of the department of industrial design. HUBO is 56kg heavy and 125cm tall, have 10 fingers, 2 eyes (vision camera), and 41 DOF. It contains a battery pack for power source and works for about fifty minutes by a charging. Also It is able to remote-control wherever network is connected.
(From Kaist)

Finally, take a look at the small but mighty HOAP-2 practicing its sumo moves. Robo-Shiko! (Shiko is the traditional sumo move in which the athlete raises his leg up high and then stomps his foot down.)

The HOAP-2 is 50cm high with 25 degrees of freedom. It has articulated fingers allowing it to grip objects. The first HOAP-2 robots shipped in July of 2003. The HOAP-2 robot is tethered and relies on an external computer and power. HOAP-2 is also a master of LINUX.
(From HOAP-2 Robot Masters Sumo And Linux. RoboShiko! )

The particular idea of a robotic wrestling companion can be found in Rolem, the exercise partner of Konstantin Kharageosis, the main character from This Immortal, created by Roger Zelazny in 1966.

Off in the distance, I heard a scream. 'Stop it, Hassan, it's not supposed to do that!' Which meant that I was Conrad, and that I was in Egypt, and that the expressionless face before me was therefore that of the golem-wrestler, Rolem, a creature that could be set for five times the strength of a human being, and was probably so set, a creature which could be given the reflexes of an adrenalized cat, and doubtless had them in full operation.

Update: Nov-02-2024: Here's a science-fictional robot fighting-machine from Jingle in the Jungle, by Aldo Giunta, published by IF in 1957:

Thirty rounds of fighting is tough work. Even for machines. Thirty rounds of fighting, at five minutes per round, is one hundred and fifty minutes, two and a half hours, of solid, shattering labor. A machine overheats the way a man does under constant stress. It’s joints expand, its lubricant thins, things begin to stick, friction wears parts. While a fight-machine’s body works against time, its opponent pounds it, jars it, jolts it. Wires loosen. Gears slip. Tubes shatter. The machine slows, becomes gawky. Its timing is a split second off. Its flexibility, its speed, are worn down.
(Read more about the robot fight-machine)

End update.

Let me know if you have any favorite robot martial arts videos, and I'll post them.