Toughness

Toughness is a Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout Tactics, and Van Buren perk.

Fallout, Fallout 2 and Fallout Tactics
With each level of this perk, you will add +10% to your general damage resistance.

Fallout 3
With this 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.

Fallout: New Vegas
With each rank of this perk, you gain a permanent +3 to your Damage Threshold. This perk is ideal for players using light armor. It is also noted that the perks Travel Light, and Light Touch goes well with this perk for those whom are using light armor.

Van Buren
Even tougher than the old Toughness! No longer just bullets and punches, now you can resist fire, plasma, and grenades!

Behind the scenes
The image for this perk is a reference to Superman, especially in Fallout, Fallout 2 and Fallout Tactics since the Vault Boy also has the Superman hairstyle.