In books such as
William Gibson's
Neuromancer and in
RPGs such as
Cyberpunk and
Shadowrun, technology has advanced far enough so that people can opt to have their
organic limbs or other body parts removed and replaced with
cybernetic replacements, or cyberware.
This can come in many forms, from basic replacement (giving someone whose legs were destroyed in battle a chance to walk again) to implementing
optional extras (giving a
netrunner a
cyberdeck with him at all times contained in his forearm). People can also have things implanted into their body that weren't there before, such as
cortex bombs for suicide missions and
datajacks for plugging additional skills into your head or accessing
The Matrix.
Usually in these games there is a
safeguard against using too much cyberware. Generally the rule is, the more cyberware you
accumulate, the less
human you feel, and in the end you succumb to cyberpsychosis, and become a raging
killing machine.
My personal favourite pieces of cyberware are cyberoptics (eye replacements which can be
customised with different vision modes) and the
Wolverine rip-off retractable claws from
Cyberpunk 2020, Wolvers.