Certain weapons and skills are absolutely essential to make it to the end of the chapter. Without them, the job will be that much harder. One great example of this is the force field, which is absolutely essential for surviving hordes of zombies.
The way that the force field works is that when any zombie hits it, it takes damage. Upgrading the force field increases the area of effect, as well as the amount of damage that it does. Typically, the fast zombies that up here in large numbers are the ones who can take the least damage before dying off, so the force field is perfect to deal with them, because they will never touch you.
For big characters and solo zombies that take a large amount of damage, the RPG is absolutely essential. This fires a missile straight at a specific enemy, and while the targeting can be funky when there’s a large crowd of zombies on the screen, the targeting will be 100% accurate when there is one boss of zombie. It will also do massive amounts of damage, allowing you to easily drain the health of the boss while you avoid its attacks.
The guardian is an excellent all-around tool, because not only does it fly circles around you and keep zombies from getting too close, but as you upgrade it, it does a massive amount of damage and more of them appear, making them an excellent weapon both against bosses and against hordes.
Weapons like a soccer ball, the baseball bat, the boomerang, and the brick may seem silly, but are excellent tools for doing large amounts of damage, and sometimes even knocking off large amounts of zombies at a time. Above all, though, you want to keep your loadout well-balanced, and you can only equip up to six skills during a single run, without the ability to swap out any of them.
When you pick up a duplicate skill, you will level it up by one more star, which increases the DPS, the AOE, cooldown speed, or sometimes all of the above. Once you get a secondary weapon to five stars, you will then be able to evolve it when you level up again. It will transform into something else; for example, the brick will transform into the dumbbell, and the force field will transform into the pressure force field.
After you unlock the evolved form of a weapon, you will be able to upgrade it again, but only one time, and the process will be a little bit more complicated. When you level up again, you will see the phrase “evolve“ followed by a weapon icon below one of the green skills. When you upgrade that green scale, the evolved weapon will also be upgraded.
The same thing is also true for your primary weapon. Your weapon can evolve into a new version of itself. For example, the baseball bat will evolve into Lucille, while the revolver will evolve into the 9MM.
Speaking of your primary weapon, keep in mind that just because the rarity of a weapon is higher, doesn’t mean that it’s automatically the one that’s going to be the most useful for you. This depends on your style of play; if you like to deal area of affect damage, then weapons like the revolver will seem terrible, but if you like to deal high DPS, then the revolver will be perfect, but the baseball bat will seem terrible.