Slayer

 is a perk available in Fallout, Fallout 2, Fallout Tactics, J.E. Sawyer's Fallout Role-Playing Game and Lionheart and a Fallout: Brotherhood of Steel skill (skills in this game work like perks do in other Fallout games).

Fallout 1, Fallout 2, and Fallout Tactics
The Slayer walks the earth! With a successful Luck roll, all of your hits in hand-to-hand combat are upgraded to critical hits - causing destruction and mayhem.
 * Note: Despite the in-game description, Slayer does not actually require a luck roll. All hand to hand attacks are upgraded to critical hits.

Fallout: Brotherhood of Steel
Each level of this skill increases your Critical Chance for +5% (up to a maximum +25) when attacking a target.

Points requirements

 * 1 Rank : 2 Points
 * 2 Rank : 4 Points
 * 3 Rank : 8 Points
 * 4 Rank : 16 Points
 * 5 Rank : 32 Points

J.E. Sawyer's Fallout Role-Playing Game
The slayer walks the wasteland! When using unarmed attacks, your successful attack rolls are increased by 30 for purposes of determining critical hit results.

Behind the scenes

 * The image for Slayer is a likely reference to Conan the Barbarian.