Old Faithful bears the Instigating effect, which does double damage if the target is at full health, making it a strong choice early in the game for stealthy characters, as a sneak attack against an enemy at full health will deal quadruple the base damage. The specific weapon modifications fitted to the gun when purchased are level dependent and will vary. As with all laser pistols in Fallout 4 it can be converted to a rifle, expanding its usefulness to Rifleman characters as well as Gunslingers and Commandos.
|Slot||Mod||Description||Modified name||Science! rank||Form ID|
|Photon exciter||Improved critical shot damage and accuracy.||Excited||-||00187AA2|
|Beta wave tuner||Adds burning damage. Improved range.||Incendiary||-||00187AA0|
|Boosted capacitor||Improved damage. Reduced ammo capacity.||Boosted||-||00187AA4|
|Photon agitator||Superior critical shot damage, accuracy and ammo capacity.||Agitated||-||00187AA3|
|Gamma wave emitter||Adds better burning damage. Better range and ammo capacity.||Fiery||1||00187AA1|
|Maximized capacitor||Better damage.||Maximized||2||00187AA7|
|Boosted photon agitator||Superior critical shot damage and ammo capacity. Better accuracy. Improved damage.||Boosted agitated||2||00187AA6|
|Boosted gamma wave emitter||Adds better burning damage. Superior ammo capacity. Better range. Improved damage.||Boosted fiery||2||00187AA5|
|Overcharged capacitor||Superior damage. Improved ammo capacity.||Overcharged||3||00187AA8|
|Barrel||Short barrel||Standard.||Short (for rifles)||-||00187A8E|
|Long barrel||Better range. Improved damage, sighted accuracy and recoil. Reduced ammo capacity. Poor hip-fire accuracy.||Long (for pistols)||-||00187A8C|
|Automatic barrel||Improved rate of fire, range and sighted accuracy. Worse recoil. Reduced ammo capacity. Poor hip-fire accuracy.||Automatic||1||00187A90|
|Sniper barrel||Superior damage and range. Worse recoil. Poor ammo capacity and hip-fire accuracy.||Charging||1||00187A92|
|Improved short barrel||Improved damage.||Improved short (for rifles)
|Improved long barrel||Better damage and range. Improved sighted accuracy and recoil. Reduced ammo capacity. Poor hip-fire accuracy.||Improved long (for pistols)
|Improved automatic barrel||Superior rate of fire. Improved damage, range and sighted accuracy. Worse recoil. Reduced ammo capacity. Poor hip-fire accuracy.||Improved automatic||2||00187A91|
|Improved sniper barrel||Exceptional damage. Superior range. Worse recoil. Poor ammo-capacity and hip-fire accuracy.||Improved charging||2||00187A93|
|Comfort grip||Improved recoil and hip-fire accuracy.||Comfort grip pistol||-||00187A94|
|Short stock||Exceptional sighted accuracy. Better recoil and aim with scopes. Improved bash.||Rifle||-||00187A99|
|Sharpshooter's grip||Better recoil and hip-fire accuracy.||Sharpshooter's pistol||1||00187A95|
|Full stock||Exceptional sighted accuracy. Better recoil and aim with scopes. Improved bash.||Rifle||1||00187A96|
|Markman's stock||Exceptional sighted accuracy. Superior recoil and aim with scopes. Improved bash.||Marksman's rifle||2||00187A97|
|Recoil compensating stock||Exceptional sighted accuracy and recoil. Better aim with scopes. Improved bash.||Recoil compensated rifle||2||00187A98|
|Improved sights||Improved focus and sighted accuracy.||Sighted||-||00187AB2|
|Short scope||Improved magnification. Superior sighted accuracy.||Scoped||-||00187AAD|
|Reflex sight||Better focus and sighted accuracy.||Tactical||1||00187AB1|
|Medium scope||Better magnification. Superior sighted accuracy.||Scoped||1||00187AAB|
|Long scope||Superior magnification and sighted accuracy.||Scoped||2||00187AA9|
|Short night vision scope||Night vision. Improved magnification. Superior sighted accuracy.||Night-vision||2||00187AAE|
|Medium night vision scope||Night vision. Better magnification. Superior sighted accuracy.||Night-vision||2||00187AAC|
|Long night vision scope||Night vision. Superior magnification and sighted accuracy.||Night-vision||2||00187AAA|
|Short recon scope||Tracks targets. Improved magnification. Superior sighted accuracy.||Recon||3||002492DC|
|Long recon scope||Tracks targets. Superior magnification and sighted accuracy.||Recon||3||00187AB0|
|Beam splitter||Splits beams into multiple projectiles covering a wider area. Poor accuracy and range.||Scattered||1||00187A9E|
|Beam focuser||Better range, accuracy, and recoil.||Focused||1||00187A9C|
|Gyro compensating lens||Superior recoil. Reduced range.||Targeting||1||00187A9A|
|Amplified beam splitter||Splits beams into multiple projectiles covering a wider area. Reduced accuracy. Poor range.||Improved scattered||2||00187A9F|
|Fine-tuned beam focuser||Superior range and accuracy. Better recoil.||Improved focused||2||00187A9D|
|Quantum gyro compensating lens||Exceptional recoil. Reduced range.||Improved targeting||3||00187A9B|
- Laser gun, the standard variant.
- Survivor's Special, a unique laser pistol with the Bloodied effect, which deals more damage the lower your health is. It is a potential reward for completing The Lost Patrol, or it can be stolen from Paladin Brandis before completing the quest.
- Good Intentions, a unique AER9 laser rifle with the Enraging effect which, on critical hits, causes targets to frenzy. It is carried by Clint.
- Prototype UP77 "Limitless Potential", a unique laser gun with the Never Ending effect, which gives the weapon unlimited ammo capacity and remove the need for reloading. It can be found in a hidden room in the University Credit Union.
- Righteous Authority, a unique AER9 laser rifle. With the Lucky effect, its critical hits do double damage and the critical meter fills 15% faster. It is given as a reward for completing Call to Arms.
- Wazer Wifle, a unique laser rifle with the Never Ending effect, which gives the weapon unlimited ammo capacity and remove the need for reloading. It is given as a reward for completing three unmarked quests for Shaun after finishing the main quest with any faction.
- Protectron's Gaze, a unique laser pistol with the Rapid ability, boosting its fire rate by 25% and its reload time by 15%. It is carried by the Mechanist.
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