A bionic arm is any cybernetic limb meant to replace the Human arm. While modern prosthetic arms are crude devices barely better than a pirate's hook, cybernetic arms seen in science fiction games are generally at least as capable as a real Human arm. For example, Kat-320 from Halo: Reach has a cybernetic prosthesis replacing her right arm, complete with shoulder, elbow, and wrist joints, and five fully segmented fingers. This arm is shown to be just as capable as her real one, and in fact she is so comfortable with it that when holding a single-handed weapon like a pistol, she carries it in her artificial right hand.
However, just as commonly as 'perfect replacements' are bionic arms that are clearly far superior to a real Human arm, capable of feats of strength and precision far surpassing that of an arm made of skin, muscles, and bone. The following are examples of bionic arms that far outshine the real deal.
Nathan Spencer's Bionic Arm is a prosthetic augmentation with immense strength and the ability to extend 20 meters as a grappling hook. He got his Bionic Arm because his arm was blown off in combat, during his rehabilitation, he became the first test subject for bionic experiments conducted by TASC., the Tactical Arms and Security Council.
Bionic Commando is a 2D platformer, but unlike other 2D platformers there no button to jump, so the player has to use the Bionic Arm to navigate around the world by grappling onto platforms, other uses of the Bionic Arm in this game is the ability to stop bullets with Nathan's Arm, and to pick up barrels and other enemies. In the top down parts of the game, players can use Nathan's arms to spin around and hit all enemies that are close.
This is a 3D game and Nathan's arm can do pretty much the same things it can do in Bionic Commando: Rearmed, as well as the ability to 'kite' enemies, also in the latest version of Bionic Commando you can pick up and throw heavier objects, such as cars, with the Bionic arm. With the arm Nathan can throw enemies and objects a lot further and into other enemies. Nathan can also Zip Kick enemies with the arm.
In a plot twist near the end of the game, it is revealed to Spencer that his arm, and all Bionic parts, are made from living people with which the subject has a strong emotional attachment. For Spencer, his Bionic Arm is actually made from his wife, who sacrificed herself so that he could have the arm, leading to the nickname 'wife arm'. The specifics of how exactly this process works is left very vague, and it is not clear if the person has their body fused into the bionic appendage, or somehow their 'soul' is imparted onto it.
Artificial limbs feature prominently in the prequel Deus Ex: Human Revolution, in which the central argument dividing society revolves around the ethics of "Human Augmentation", the science of enhancing the human body through cybernetic implants. The protagonist, Adam Jensen, is near-mortally wounded during a terrorist attack, and must receive augmentation in order to save his life. This includes removing his crippled arms and replacing them with cybernetic prosthetics; these arms have razor-sharp blades built into the forearms that allows Jensen to swiftly and permanently deal with an enemy if he gets up close and personal. In addition, he is also gifted with superhuman strength to the point of being able to knock out any normal opponent with a single punch. With the right upgrades, his bionic arms are also capable of punching through solid walls, carrying twice as much gear as an un-augmented Human, and lifting and throwing heavy objects like dumpsters, vending machines, and refrigerators with ease.
By the time period of the original game, Deus Ex, physical augmentation of the kind given to Adam Jensen has become obsolete; protagonist JC Denton is among the first field operatives to be gifted with nanotechnology-based augmentation. These nanomachines strengthen the user's muscles and fortify their bones, among other things, allowing someone whose entire body is still flesh and blood to be capable of the kinds of superhuman feats previously reserved for those whose bodies were mostly machine.