Bill

Bill, or Bill Overbeck is one of the Survivors, a Vietnam veteran with combat skills that have helped keep him alive, he is also the oldest of the group. In official media, he is usually seen wielding the assault rifle, probably to compliment his backstory.

Official description
It took two eventful tours in Vietnam, a handful of medals, a knee full of shrapnel, and an honorable discharge before the unthinkable happened: Bill ran out of wars. But now an army of infected undead has declared war on humanity. After decades of aimless drifting and dead-end jobs, Bill's finally gotten back the only thing he ever wanted: an enemy to fight.