The Streets

In "The Streets" the Survivors follow the helicopters from the hotel as they head towards the evacuation center at the mall. This chapter contains a Crescendo Event in which the Survivors must obtain a pack of cola from a Save 4 Less convenience store with an alarmed door for the owner of a nearby gun store, who returns the favor by clearing the roadblock that prevents the Survivors from reaching the mall with a grenade launcher.

Whitaker's Gun Shop
Half way through the chapter, you'll come across a gun store under the ownership of Whitaker that contains 3 or more of every gun in the game(except for the grenade launcher), an ammunition pile, 2 melee weapons, 2 first aid kits, and laser sights.

Trivia

 * Save 4 Less is likely a reference to the name of the game.
 * Save 4 Less may also be a reference to a chain of super markets known as Food 4 Less
 * In Whitaker's store, the Tactical Auto Shotgun is labeled as "fully automatic", when it is only semi-automatic.
 * The gun store might be inspired by Dawn of the Dead (2004), since it also contains a gun shop nearby with a Survivor in it and it is close to the Mall. In both the film and the game, the survivors risk death to deliver something trivial to the gunshop owner. In Left 4 Dead 2, this was cola. In Dawn of the Dead, it was a sandwich.
 * When you melee several times with the cola, then deliver it to the gun shop owner and let him shoot the barrier and wait a few more seconds, you can hear him open the cola. If done right, you can also hear the cola spewing from the bottle and over him.
 * It's a wonder why Valve made a model of the Gunshop Owner is beyond anyone as people with expect no model to be made since you can't really see the model.