How do you switch weapons on world at war zombies?

In Call of Duty: World at War Zombies, you can switch weapons by pressing the corresponding button for your secondary weapon. On most platforms, this is typically the "Y" button on Xbox or "Triangle" on PlayStation. If you want to pick up a new weapon from the ground, simply walk over it, and your current weapon will be replaced. Additionally, you can use the Pack-a-Punch machine to upgrade your weapons for improved performance.