Adrenaline Rush

Adrenaline Rush is a Fallout 2, Fallout Tactics and Lionheart perk. It is also a skill that was to appear in the canceled Fallout: Brotherhood of Steel 2 (skills in this game work like perks do in other Fallout games).

Fallout: Brotherhood of Steel 2
When HP drops below 40% Melee attacks do more damage.

Lionheart
You will gain +1 to Agility and +20 evasion if your hit points drop below half of their maximum and an additional +1 to Agility and +10 evasion, +1 melee dmg if they drop below 25%.

Behind the scenes
The Fallout 3/Fallout: New Vegas/Fallout 4 perk Nerd Rage! is similar to Adrenaline Rush, and uses a variation of the image.