Rad Child (Fallout: New Vegas)

Rad Child is a Fallout: New Vegas, Fallout Tactics and J.E. Sawyer's Fallout Role-Playing Game perk and Fallout: Brotherhood of Steel skill (skills in this game work like perks do in other Fallout games).

You do not take immediate damage from radiation. In fact you gain extra healing while being exposed to it! However, radiation continues to build up in your system as normal.

Fallout: Brotherhood of Steel
With this skill, Cain restores HP whenever he takes radiation damage.

Trivia
Rad Child could possibly be a reference to the Iron Maiden song "Wrathchild"

Fallout: New Vegas
Healing bonuses only apply when irradiated:

HP +2 HP +4 Critical radiation poisoning - HP +6 Deadly radiation poisoning  - HP +8

It's worth noting you will still die when you reach 1000 rads