Forbidden topics

     As a teacher, I've seen my fair share of essays on topics that I don't want to deal with any longer. I've even known teachers to create a list of banned topics such as abortion and capital punishment. I think it's mostly because students all say the same thing over and over and over and over and over and over and over and over and over and over again. Without a new take, a new, fresh perspective, I'm tired of it. Yet I haven't created a banned list yet. Emphasis on yet. I find myself leaning in that direction, though, as I will groan after just a few lines because I can already tell that there's nothing new to read.
     I've seen a few agents post about how they're tired of certain stories. Vampires readily come to mind as I've seen agents post on those a time or two, and I understand that agent inboxes are clogged to the RAM with queries for them. I'm sure there are others, so I wonder, and ask (politely of course) what topics make agents groan even within the genres they accept? Also, would it be possible for a fresh, new perspective on such a topic to grab an agent, or is it too late by the second line of the query?