Headphones
This one had a little bit of argument about whether or not it is necessary for camping. I maintain that it isn't which is odd because I am both a big music person and also someone who does not appreciate other people playing their music while camping and I don't get the wonderful sounds of nature. Hiking_FreedomFlower on the other hand feels that they are very necessary. She uses them constantly, while running, biking, hiking...
They do have multiple uses outside of not angering the other campers. You obviously can listen to music, but one of my favorite camping activities is reading and headphone would allow for me to listen to audio books which is a big plus. Most of them will allow you to talk on your phone without having to fumble around with the phone itself.
There are a few different kinds of headphones. There are the big padded ear covering headphones which are largely used for noise cancelling. There are the cheaper earbuds which go on the inside of the ear. And, there is the bone conducting earphones which instead of blasting sound into your ear canal it vibrates the bones of the ear so you can hear everything from the headphones as well as the outside world.
There are similarities between them all such as they all can be wireless if you want, different colors and styles, and price ranges. I am a huge fan of this third option. I feel the noise cancelling variety takes away from the natural setting of camping. Earbuds often hurt peoples ears, you can lose the little rubber ends in your ear, and they can get quite dirty. The bone conducting headphones are great because you still hear all those nature sounds while listening to your music or book. They sound odd, but they work very well and I find them to be very comfortable.