Currently, we have the following official reasons to close a question:
Duplicate
Off topic due to:
General Programming Question
No objective winning criterion
Belongs on another site
Unclear what you're asking.
Too broad
Primarily opinion based
However, there are other valid reasons to close a question, which are not in the close interface, due to space limitations or otherwise. I think it would be a good idea to make a list of such reasons here. These are things to look out for when considering closing a question, even though they're not common enough to warrant a custom entry.
Here are some such reasons:
Are there other important categories that we should keep in mind, even though they don't come up enough to have their own close vote entries?