Nerd Rage!

Nerd Rage! is a Fallout 3 and a Fallout: New Vegas perk.

Fallout 3
Whenever your Hit Points drops to 20% or below, your Strength is raised to 10 and you gain 50 to damage resistance. This stacks with other perks, and applies regardless of clothing, which makes it still useful even if you wear heavy armor, as it can help maintain your DR even if said armor is damaged or broken.

Fallout: New Vegas
Whenever your health drops to 20% or below, your Strength is raised to 10 and your damage threshold is boosted by 15. As in Fallout 3, this effect stacks with similar bonuses, and applies even if you're naked or your armor is broken; you merely need to meet the health threshold.

Notably, the Courier's base health determines the trigger for this perk. Bonus HP from other sources such as Buffout or Thought You Died (perk) will not raise the threshold.

Behind the scenes

 * The perk is based on Adrenaline Rush, a perk which had first appeared in Fallout 2. The art is also borrowed from Adrenaline Rush, save for a few thematic changes.
 * The Vault Boy image is a reference to the Incredible Hulk, whose clothes become shredded during his transformation.