The Church Guy is a minor character in "Left 4 Dead", he is encountered in the safe room at the end of the third chapter "The Church" of Death Toll, he was as well the only survivor in the fictional town of Riverside. He is never really seen until he became infected.
He is one of the survivors during the outbreak in "Left 4 Dead", he locked himself inside the safe room. It is revealed that 1 hour before the Survivors came, he been bitten by another person who claims to be immune, he then thinks and tries to ocnvince himself he is so.
Left 4 Dead
Players encounter the Church Guy at the end of the third chapter in "Death Toll", when a Survivor tries to open the door, he refuses, stating he will not let them in until he is sure that their immune. He gives them a "test" to pass: he rings a bell, attracting a horde of zombies (the Crescendo event of the chapter). After the Survivors survive the attack, the Church Guy starts grudling, growling, and coughing. When the survivors finally open the door, he has already turned into either a Boomer, Smoker, or Hunter, depending on what was heard when the door is opened.