Using a firearm will make taking down your enemies way more manageable than if you tried to fist fight your way through the crystallized enemies, but they have a handy use once the ammo clip is empty. When it flashes up on the screen that you’re out of ammo you can then throw your weapon by hitting the right bumper on your controller or with the right click of your mouse.
This will stun your enemy and in some cases make them drop the weapon they were holding, giving you a bit of time to pick up another weapon and get a shot in. You can also use this to your advantage when in a tight spot. If you’ve got a bullet coming your way and are out of ammo, you can throw your weapon at the oncoming projectile and smash it into tiny pieces. A handy little tip for when you get yourself into a sticky situation.