10ft Micro-USB Charging Cable
My biggest pet peeve is some smartphones come with 3ft charger cords that aren't even long enough to go from the wall outlet to my desk, the bed, or anything else for that matter. Thankfully the Note 5 has a long 5ft cord, but I wanted one even longer.
I have about 5 of these Anker 10ft Micro-USB cables, and they're amazingly useful for around the house, traveling, and everything else. If you've never bought a quality (not a cheap colorful one) 10ft charging cord, this will change your life. Especially once you learn to love the 10ft ones.