Binoculars

From the Metal Gear Wiki

The binoculars, or scope, are long-range, lightweight scouting devices. Used constantly throughout much of the Metal Gear series.

In Metal Gear, these will allow Solid Snake to see one screen in any direction from his current location. Same goes for the binoculars in Metal Gear 2: Solid Snake.

Metal Gear Solid/The Twin Snakes allows for first person viewing and control. Pressing the Punch button zooms in, and the Weapon button zooms out electronically. Raiden uses the same type of scope in Metal Gear Solid 2.

A pair of binoculars are used by Naked Snake during the Virtuous Mission and Operation Snake Eater. Made especially for the U.S. military by Sigint. They are strong, waterproof, and are filled with nitrogen gas to prevent lens fog. The eyepiece, objective lenses, and prism have been coated to reduce glare and can work fairly well in dark places. The weight is 1.0kg., or 2.2 lbs. It's also available in Metal Gear Solid: Portable Ops

Instead of using binoculars in Metal Gear Solid 4, Old Snake uses the Solid Eye.

The cameras and sniper rifles can make great substitutes.