L4D2 NPC's and Infected Rejected Out Of Hand

Oil Derrick Worker:
You never see them, because, well, they're kinda isolated, but you hear reports about them, and they sound terrifying.

Tai Chi Master
If you ever swing that ax faster than an heavily sedated sea sponge, he goes down immediately. But should you go slower, HOO EEEEE!.

Hipsters
You only ever encounter their corpses, they go first.

Vegan
He can be found dumpster diving, looking smug and eating rats.Organic rats.

Flautist
A jazz flautist.

Driver
Sits in his car, a well-notated map of Toledo in his lap, a cold cup of coffee on the dash, and him, crying softly.

Concierge
He stands, looking from the door to his front desk, torn behind a hunger for human flesh and a sense of duty.

Gymnast
Stands below the double rings, arms still on the rings, him looking up, moaning.

Foodie
Fusses and pats you down, emits a low 'humming' noise as he considers, invariably leaves you alone.