Secondary weapons are your emergency weapons. If you run out of ammo in your primary or just run out of clip ammo and want to save yourself from reloading a slower reload weapon, your secondary is your best friend. But if you're running a mission that requires you to hold a key mission item like a Power cell or the receiver box for Mobile defense, your secondary is your only other option for longer ranged combat. Secondaries could range from Pistols, Kunai, Sidearm variant of shotguns, and Charge weapons.