Francis, Zoe, Bill, and Louis aren't the real characters in Left 4 Dead. These guys are:

Shotgun Sally:
- Convinced the shotgun(s) is the be all end all
- Uses the Shotgun at long range
- Thinks peeling zombies off you with the shotgun is a good idea
- Usually likes to stand in the back

Ricky Rambo:
- Runs ahead of the pack no doubt trying to race to Zombie Genocide
- Complains when he gets jumped by a Zombie Special
- Usually also a Shotgun Sally
- Upon death proceeds to abuse team about how noob they are for not keeping up
- Always rushes the people in the lobby, even if there is only you and him

Health Pack Harry:
- Never shares pills and/or health packs
- Heals himself from yellow health whilst you stand there with red health
- Sometimes a Ricky Rambo

Car Alarm Carl:
- Shoots the car alarm... everytime
- Will run back from the safe room, just to shoot the car on the apartments map

Check out the original post on the Left 4 Dead forum for more. If there are any of these you don't get, that means you're that guy.

Thanks wisefool.