Feat: Wounded Fury

Prereq: Constitution 15+, Rage class ability
Benefit: When reduced to to 50% or less of your hit points in battle while in a rage, you gain a +2 bonus to attack and and damage rolls and a +2 bonus to saving throws against spells and spell like effects. When reduced to 25% or less of your hit points these bonuses become +3.

Source: Conan: Hyboria's Fiercest pg 72, Mongoose Publishing
http://www.mongoosepublishing.com/home/series.php?qsSeries=7