Crazy Cat Lady: the living quarters of the murderous airport couple is littered with cats.
Crippling Overspecialization: Bangley knows almost nothing about anything except building and using weapons. He relies on Higs for everything else. Subverted, as Higs eventually discovers that Bangley was raised a farmer and has a whole wealth of useful skills that he's refused to acknowledge.
Evil Old Folks: the couple living in the airport, who lure pilots to their doom.
From Nobody to Nightmare: Bangley was no one of consequence or training before the end of civilization. Now he's a bloodthirsty one-man-army with countless notches on his belt.
Last Name Basis: Bangley, who never tells Higs his first name even after nine years of living together. Higs has to find out from someone else.
Last Stand: Bangley has one while Higs is away when their home is attacked by a large group of raiders. He manages to kill all of the intruders and survives long enough for Higs to return with medical aid.
Riddle for the Ages: Where did the flu come from? Where did the blood virus come from? Why is the environment changing? What the deal with the Arabs?
Sociopathic Hero: Bangley cares only about survival and seems to get a kick out of killing people. Luckily he's on Higs's side.
Wanton Cruelty to the Common Comma: Higs's narration uses extremely idiosyncratic punctuation, apparently to represent his erratic mind. He's an educated man, and an aspiring writer, so we know that he could punctuate properly if he were actually writing it down. Spoken dialogue is always formatted according to standard English.
Warrior Poet: Higs is a gentle soul, but can kick ass when he really needs to. He was also an aspiring poet at one point and still thinks about poetry.