Any character or enemy with a Sniper condition will have his luck attribute doubled. A higher luck attribute increases the chance for critical hits.
Note: Sniper, as well as other positive conditions, will automatically time out after awhile (unless you have it crafted to the equipment you are currently wearing, which renders it permanent). You can review all of your character's status conditions in the status menu. During battles, all characters and enemies are marked with their active status conditions.
NOTE: Sniper condition stacks with the Sniper Master skill.
Items that give you the Sniper condition:
Gift of Thunder
God Ray Scythe
God Ray Scythe+
Twist of Fate