This list contains multiplayer first- or third-person shooters that you don't need to buy to play. Even though they are completely free, they still allow you to spend money on various cosmetics and boosters.
Usually in this type of “shooting games” there are many modes, and new content (missions, weapons and mechanics) is constantly appearing in them. Some of these shooters have a separate client, and some can be downloaded through Steam or the Epic Games Store.