I think Stocking stuffers are one of my favorite gifts during Christmas. I don't have to wrap anything and I can fit a lot of smaller items inside. I've made a list of some of my favorite Stocking Stuffer ideas for adults that I think you'll like. You can sort the stocking stuffers by gifts of him or her.
Some of my favorites include the Une Bobine iPhone charger. It's a coil that is adjustable so that you can bend it and shape it into the form you want. I like to plug it into my computer and have it stand up next to it. It's like having one of those cellphone stands but it charges as well.