The Overwatch hero with a mechanical eye who uses a sniper rifle is Ana. Her full name is Ana Amari, an Egyptian marksman and one of the original founders of the Overwatch organization.
Ana is a Support hero whose weapon is the Biotic Rifle, a long-range sniper rifle that damages enemies and heals allies. Its shots can affect teammates and opponents differently, allowing skilled players to support their team from a distance. Her other abilities include Sleep Dart, which temporarily disables an enemy, and Biotic Grenade, which heals allies while preventing enemies from receiving healing for a short time.
Ana lost her right eye during a confrontation with Widowmaker, formerly her friend Amélie Lacroix, during a hostage-rescue mission. Ana survived the shooting but allowed the world to believe she had died, later returning to combat when new threats emerged.
The answer is sometimes confused with Widowmaker because both are associated with sniping and eye injuries. Ana is the support sniper: she combines precision shooting with healing, crowd control, and the Nano Boost ultimate.