For multiple recent questions, people have wanted to close a question because the question was too narrow - not enough variety of potential answers to make it interesting.
Those questions were: Sign that word!Sign that word!, , and Fibonacci in +!()[]scriptFibonacci in +!()[]script.
The desire for such a close reason has come up before, leading to Too trivial Close Vote, where the clear most upvoted option was adding the following:
Too Narrow
There are either too few possible ways to answer, or answers would only differ in the language used.
Would it be possible to add this close reason, or is there something preventing us?
If we can't add that close reason, what should we do if we encounter such a question, and would like to vote to close it?