Scarf

A Scarf is a piece of fabric worn around the neck for warmth, sun protection, cleanliness, fashion, or religious reasons. It is a common type of neckwear. They can also at times be used for camouflage purposes, similar to Balaclavas.

Sandinista National Liberation Front/South American guerillas
Kazuhira Miller during the Peace Walker and Ground Zeroes incidents wore a yellow scarf around his neck due to his formerly commanding a guerilla unit in Colombia before joining the Militaires Sans Frontieres.

The Sandinistas wore yellow scarves as part of their uniform.

The Marxist revolutionary Che Guevara was mentioned to keep a scarf from his second wife Aleida as a keepsake after she fell in battle.

Venom Snake
During his activities in 1984 shortly after his escape from the Hospital at Cyprus, Venom Snake took to wearing a scarf during operations within Afghanistan, due to the arid environment of the region and the presence of sandstorms, and to a lesser extent Central Africa due to the heat of the area.

40th Army
The Soviet 40th Army during their activities in Afghanistan sometimes adopted scarves covering all but their eyes, for the reason why Venom Snake wore a scarf during his activities there.

Militaires Sans Frontieres
The MSF survivors who got sucked into a pocket dimension shortly after the events of the Ground Zeroes Incident frequently adopted the use of similar scarves to that of the leader of Diamond Dogs, Venom Snake. Their scarves came in at least four colors, all of which were given a metallic luster: Blue, Pink, Green, and Silver.

Middle Eastern militiamen
The militias in the Middle East during 2014 wore shemagh scarves due to both their holding to the Muslim religion, the arid nature of the environment, and as a form of camouflage similar to balaclavas.

South American rebel soldiers
The South American rebel soldiers during 2014 at times wore scarves during their operations in South America, which were generally colored black. These only served to mask their identity.

Behind the scenes
The Metal Gear Solid 4 Database erroneously refers to the Handkerchief item from Metal Gear Solid as being Sniper Wolf's scarf.

Scarves made an appearance in the series starting with Metal Gear Solid 4: Guns of the Patriots.

The player could purchase scarfs modeled either after the shemagh scarves of the Middle Eastern militiamen or the scarves worn by the South American rebel soldiers in Metal Gear Online.

The player can technically wear a scarf when wearing either the Miller or Amanda outfits in Metal Gear Solid: Peace Walker.

Scarves have a formal debut as a gameplay element in Metal Gear Solid V: The Phantom Pain, where the player can equip Venom Snake with a scarf for missions, provided that he is wearing camo fatigues as his uniform. They also appeared to a certain extent in Metal Gear Online 3 via the Tactical Scarf equipment. They will make a return in Metal Gear Survive for similar purposes to in Metal Gear Solid V, with four of them acting as pre-order bonus DLC.