Most night shift jobs. A friend of mine worked as a concierge at a fancy building doing overnight shifts. She basically just sat there all night listening to podcasts. Someone might get locked out or there might be a noise complaint, but that was usually it. If you can manage the hours, that kind of work seems like a great opportunity to write a lot of code.
Aren't you supposed to pay attention and watch out for danger in such a job?
The great lie of security. At the level where much (most) of security operates, you're lucky not to have serious breaches of conduct generated from unending boredom.
You are supposed to. In reality, many don't. If you're client facing or have cameras on you, you can be fired for not paying attention (or at least looking like you are).
Also, depending on your location it can be a very dangerous job (I believe more security officers are killed than police officers nationally).