The Survivors

There are four playable human characters in the game, each with a different and unique appearance to make it easier to identify which character you are looking at when you aren't close enough to recognize the face. Each player is randomly assigned a character when they join the server and each character has the same abilities and may use the same weapons.

Francis
The tattoo-covered biker. He knew Bill before the outbreak of infection as well, which may mean they both went to Vietnam.

Zoey
The teenage daughter of a wealthy family. Zoey's face is modeled from Alesia Glidewell, the same person Chell from Valve's Portal was modeled from.

Bill
A Vietnam veteran with combat skills that have helped keep him alive, he is also the eldest of the band of survivors.

Louis
An assistant manager at a local retail electronics chain store.

"churchguy"
A man who's only evidence of existance in L4D is his voice clips in the Demo. He appears to be afraid of infection, locking himself in some sort of way that the survivors must get through. Further investigation into his clips show that he was bit, and waited an hour, so he deemed himself immune. Ultimately, he becomes an infected.