Pitt Fighter

Pitt Fighter is a perk added to Fallout 3 in the The Pitt DLC.

"The vicious fights in the Hole have left you stronger. Both your damage and radiation resistance have been increased by +3%."

The Player can get it by completing the Pitt Battle. This perk increases your Radiation Resistance and Damage Resistance by 3%.

Trivia
The image for this perk depicts Vault Boy wearing armor identical to what Blaster wore in the film Mad Max: Beyond Thunderdome.

Similarly, the helmet of Vault Boy looks strikingly similar to Isaac's helmet from the game "Dead Space".

Or, the helmet could be an in-game referance to the Eyebot Helmet