Ant Might (Fallout Supplement)
From D&D Wiki
All your fights with Fire Ants have made you tougher and given you the ability to better resist fire.
Prerequisite: Kill 30 Giant Fire Ants in one on one combat, no help you gotta do this on your own!
Benefit: +1 Strength, Resist Energy Fire 10, +2 on Reflex Saves to put fire out.
Special: The effects of this feat stack with the Ant Sight feat.