Toughness

Toughness is a Fallout, Fallout 2, Fallout 3 and Fallout Tactics perk.

Fallout, Fallout 2 and Fallout Tactics
When you are tough, you take less damage. Each level of this perk adds +10% to your general damage resistance.

Fallout 3
With the Toughness perk, you gain +10% to overall Damage Resistance, up to the maximum of 85%. You will also gain a unique dialogue option when talking to Ted Strayer during the You Gotta Shoot 'Em in the Head quest.

Behind the scenes
The image of this perk is a reference to Superman.