There's nothing I love more than to watch the friendly serial killer Dexter at work. FYI, he only kills people that kill other people so somewhere somehow you manage to empathize with him to a certain extent. By day he's a blood analyst, by night he's out setting the world to rights. And when he's not, he's taking care of his adorable little son.
If you ask me, it's the best show on TV. The suspense kills you which is why I recommend buying or downloading entire series and watching them in one go on a rainy day.