A former medic from the NCR, now serving as a doctor in the Powder Gangers. Before he was a medic or a powder ganger, Hannigan worked as a farmhand, bouncer, a bandit and an NCR trooper. After becoming a medic he was incarcerated for selling NCR medical supplies on the black market. Being a "doctor", with 6 months of medic training, for the Powder Gangers gives him an excuse to not have to do any fighting because "The gang can't afford to lose its only doctor".
"I was an NCR medic for six months, so I'm not exactly a "doctor." Still, it's more medical training that any of the other guys here. It also gives me an excuse to stay out of any raiding parties. The gang can't lose its only doctor now, can it?"