A shaver is a type of device that is used to remove facial hair, or in some cases, sideburns. They mostly come in razor varieties, although electric versions are also common.
Use by Solid Snake
A generic electronic shaver was found lying around in Big Shell's Strut A Deep Sea Dock by Raiden, in 2009. Despite having no obvious use, Raiden took it anyway and carried it around until he met up with Iroquois Pliskin, who gave Raiden a SOCOM and a pack of cigarettes. Raiden in return handed Pliskin the shaver as a token of his appreciation. After infiltrating Arsenal Gear, Pliskin, who was actually Solid Snake, used the shaver to shave himself before meeting up with Raiden.
Behind the scenes
The Shaver is an item that appears in Metal Gear Solid 2: Sons of Liberty. If the player manages to find the Shaver and does give it to Snake in Strut B, Snake will be clean-shaven when Raiden meets up with him within Arsenal Gear, giving him a similar look to his appearance from the first game.
Despite the Shaver being available on all difficulties in the original version of Metal Gear Solid 2, it was turned into a special item in the Metal Gear Solid 2: Substance, where it now only appears on Hard, Extreme and European Extreme difficulties. Why this was done is unknown.