Die Hard (Fallout: Brotherhood of Steel)

Die Hard is a Fallout Tactics, Fallout: Brotherhood of Steel and Lionheart Perk.

Fallout Tactics
You don't give up easily. When your hit points get below 20% you get an additional 10% to damage resistances.

Fallout: Brotherhood of Steel
Each level of this perk increases your health for +20 (up to a maximum +200) hit points.

Points requirements

 * 1 Rank : 4 Points (+20 Hit points)
 * 2 Rank : 8 Points (+50 Hit points)
 * 3 Rank : 16 Points (+90 Hit points)
 * 4 Rank : 32 Points (+140 Hit points)
 * 5 Rank : 64 Points (+200 Hit points)

Lionheart
When your hit points get below 20%, you gain +20% to all resistances and your armor class goes up by 5.