Earplugs (2 sets)
Gun fire should be your last resort. If you are smart you will still be working on self-preservation. There is no point in surviving if you are going to let your human machine become inoperable. If you are facing off against biters or enemy humans it could come to gunfire. If you stand beside weapons that are firing continuously your hearing will suffer.
Do you want to become dinner? Go to bed with ringing ears. You won’t be able to hear an elephant approaching, let alone zombies. Look for earplugs that come in a protective case. This variety will keep them dry and safe. Earplugs will not be something you will run into often on the road.
You may also have a talker in your group of survivors. Talkers can be as bad as walkers. Earplugs come in handy then as well.