Area of Responsibility – Home
Put it in one of your areas of responsibility. For me it would be my Area titled Home. Very, very few software systems (online or desktop) support areas of responsibility (nozbe not being one of them) and for me, it's just as essential as a Projects list.
Also, make sure it isn't a project in disguise. Have you already purchased the light bulb in question? Do you know where it is? Do you need to go to the hardware store first? Could/should you need to send someone else to the hardware store? What kind of light bulb is it? Have you been considering purchasing a different type of light bulb? Would now be a good time to change? etc.
Those are just questions to help you plan. You may know the answers off the top of your head but hey, maybe not. If not, then it is probably a (tiny) project, not just a next action. [All the same, if it is a project, it should still go in your area of responsibility (probably) titled "Home."]
Definition of Project – Any outcome you want that requires two or more action steps.
Hope that helps!
:-D