Finesse

Finesse is a Fallout, Fallout 2, Fallout Tactics, Van Buren and Lionheart Trait, as well as a Fallout 3 Perk.

Trait
Your attacks show a lot of finesse. You don't do as much damage, but you cause more critical hits.

Fallout and Fallout 2
All of your attacks do -30% damage. Your critical chance is increased by 10%. Technically, this is done by adding a +30 DR modifier to all attacks, which is ignored by armor-bypassing criticals. And because criticals have a chance to kill an enemy instantly anyway, this is a very good trait.

Fallout Tactics
All of your attacks do -25% damage. Your critical chance is increased by 10%.

J.E. Sawyer's Fallout RPG

 * -2 to damage, +2 to attack rolls for purposes of determining critical hit results.

Fallout 3
You have a higher chance to score a critical hit on an opponent in combat, equivalent to 5 extra points of Luck, or 5%.