Sunglasses

Sunglasses, informally referred to as "shades," are a type of eyewear worn by various people. As the name suggests, they are used to block out the rays of the sun via tinted-colored glass. They could also be used by blind people to indicate that they either are unable to see or that their blindness comes from a disfiguration. There are a variety of forms of sunglasses, including aviator sunglasses or sun visors.

Usage
Kazuhira/McDonnell Benedict Miller, also known as Master Miller, was known to wear Aviator Sunglasses most of the time, even wearing them during instances where they wouldn't work, such as indoors or while driving in a thunderstorm. Strangelove also wore sunglasses during the 1974 Peace Walker Incident, apparently due to her albinism. Several of the soldiers under the employ of the CIA mercenary group Peace Sentinel also wore sunglasses while indoors. In 2014, Liquid Ocelot wore sunglasses during his business operations with the PMC Mother Company Outer Heaven. Johnny Sasaki, going by the codename Akiba, also wore a sun visor, apparently to keep himself fully enclosed due to a paranoid nature. Even after ditching the balaclava, he still retained the sunvisor. In 2018, during Maverick's mission into Africa, Raiden also wore sunglasses while meeting with the prime minister, complete with a suit. However, he discarded them when fighting cyborgs that ambushed them.

Behind the scenes
In Metal Gear Solid, Liquid Snake wore sunglasses while disguising himself as Master Miller, something he also briefly referenced to Snake when the latter escaped from a death trap when the ruse was exposed. However, it is left ambiguous as to whether it actually occurred or if it was one of the Metal Gear-series standard fourth wall breaks.

In Metal Gear Solid 2, sunglasses are unlockable if the player manages to collect some dog tags during either the Tanker or Plant Chapters. In addition, the Document of Metal Gear Solid 2's script and the Grand Game Plan indicated that the Dead Cell members (then known as Black Cell) were originally supposed to wear shades, although this was cut from the final version.

In Metal Gear Online, the player can unlock Liquid Ocelot's and Johnny Sasaki's respective sunglasses with enough DP.