Sniper

Sniper is a perk in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout 4, Fallout 76, Fallout Tactics: Brotherhood of Steel, Fallout: The Board Game, and J.E. Sawyer's Fallout Role-Playing Game.

Fallout, Fallout 2 and Fallout Tactics
You have mastered the firearm as a source of pain. With this perk, any successful hit in combat with a ranged weapon will be upgraded to a critical hit if you also make a Luck roll. It adds another Luck roll of (10*Luck), hence having 10 LK converts every hit to critical and indirectly causes target's armor DR to be ignored regardless of player weapon. The perk synergises extremely well with weapons capable of burst fire, as every shot in one burst is upgraded. Taken in combination with Better Criticals' 20% chance for insta-kill, it makes burst mode extremely deadly.

Fallout 3, Fallout: New Vegas
With the Sniper perk, your chance to hit an opponent's head in V.A.T.S. is increased by 25%. As with most perks that increase your chance to hit in V.A.T.S. this bonus is multiplicative, not additive. For example, if you had a 50% chance to hit an enemy's head without the perk, you would have a 62.5% chance with the perk. In Fallout: New Vegas, this perk is useful for counter-acting the Fast Shot trait.

Fallout 76
Sniper is a perk in the Nuclear Winter battle royale mode.
 * Nuclear Winter

Fallout: The Board Game
Once discarded, any fight action performed for the rest of the turn can be used to target any enemy on the world map, as long as the player character is equipped with a ranged weapon.

J.E. Sawyer's Fallout Role-Playing Game
You don't waste bullets on flesh wounds. When using firearms, your successful attack rolls are increased by 30 for purposes of determining critical hit results.

Bugs

 * In Fallout Tactics, version 1.27 does not produce the advertised result of the Sniper perk. The perk is obtainable but appears to be bugged (tests with 10 LK have failed to produce any noticeable increase in critical strike rate, which should produce a 100% critical strike rate).
 * In Fallout 4, while sneaking, the combination of the first rank of Sniper and wearing armor with Stabilization mods on both arms is enough to stop virtually all sway when looking down a sniper scope. However, this may stop working. Having the Cloak & Dagger perk may contribute to this bug.
 * Using the console to first remove each level of the Sniper perk and then reapply them may fix the issue. For someone with all 3 ranks in Sniper, the commands run after opening the console with ~ would be:
 * (removes 3rd rank)
 * (removes 2nd rank)
 * (removes 1st rank)
 * (adds 1st rank)
 * (adds 2nd rank)
 * (adds 3rd rank)

Gallery
Heckenschütze Francotirador Sniper (compétence) Snajper Снайпер Снайпер