All of the Left 4 Dead survivors, rigged up for Guitar Hero: World Tour - Definitive Edition.

Official descriptions:

Louis: Louis had been working up the courage to quit his job as Junior Systems Analyst at his company's IT department when a virus showed up and downsized the world. Now Louis has a new set of goals (live long enough to succeed) and a new set of tools (guns, sharp objects) to help him achieve them. With any luck, he'll figure out how the new management operates before they get a chance to murder him.

Bill: 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 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.

Francis: Cocky, loud, and pretty sure he's indestructible, Francis acts like the zombie apocalypse is the world's biggest bar fight. When the virus hit, everybody else stockpiled food and looked for a place to hide. Francis found a gun and had some fun. No cops, no laws, no order—if it wasn't for all the zombies, he could almost get used to life like this.

Zoey: After spending her first semester holed up in a dorm room watching old horror movies, Zoey was given a choice: Stop fooling around and get her grades up, or drop out. Now that the planet's overrun with murderous zombies, and all of her professors are dead, Zoey at least has the cold comfort that she's been studying up on the right subject after all.