Sight Mods actually come in two flavors, Sights and Scopes. Though High-Caliber weapons are the only ones to get a visual overlay scope, all weapons can benefit from a change to the level of zoom or one of the other effects offered.

Scope Overlays
Sharpshooter Scope Overlay
Sharpshooter Scope Overlay
Commando Scope Overlay
Commando Scope Overlay
Explosive Acceleration Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Rocket Launchers and Detonators. Mod Effect: Projectile Velocity.
Explosive Magnification Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Rocket Launchers and Detonators. Mod Effect: Blast Radius.
High-Caliber Accurate Commando Scope
Scope that provides a lower level of zoom than the base scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Accuracy.
High-Caliber Accurate Marksman Scope
Scope that improves firing behavior without changing the scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Accuracy.
High-Caliber Accurate Sharpshooter Scope
Scope that provides a higher level of zoom than the base scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Accuracy.
High-Caliber Persistent Commando Scope
Scope that provides a lower level of zoom than the base scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Falloff Distance.
High-Caliber Persistent Marksman Scope
Scope that improves firing behavior without changing the scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Falloff Distance.
High-Caliber Persistent Sharpshooter Scope
Scope that provides a higher level of zoom than the base scope. Attachable to Bolt-Action Sniper Rifles, Semi-Auto Sniper Rifles, and Pistols. Mod Effect: Falloff Distance.
Mid-Caliber Accurate Commando Scope
Scope that provides a low level of zoom. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Falloff Distance.
Mid-Caliber Accurate Marksman Scope
Scope that provides a mid level of zoom. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Accuracy.
Mid-Caliber Accurate Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Accuracy.
Mid-Caliber Persistent Commando Scope
Scope that provides a low level of zoom. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Falloff Distance.
Mid-Caliber Persistent Marksman Scope
Scope that provides a mid level of zoom. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Falloff Distance.
Mid-Caliber Persistent Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Assault Rifles, SMGs, and LMGs. Mod Effect: Falloff Distance.
Shell Accurate Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Combat Shotguns, Pump Shotguns, and Sawed-Off Shotguns. Mod Effect: Accuracy.
Shell Persistent Sight
Sight attachment which improves firing behavior without adding a scope. Attachable to Combat Shotguns, Pump Shotguns, and Sawed-Off Shotguns. Mod Effect: Falloff Distance.