You can closevote your own questions if they're not up to the site's quality expectations. You automatically unlock this privilege at 250 reputation, and it has been around for a while now. As said in the Privileges page:
When should I close my own question?
Questions that are sufficiently off-topic, as outlined in the FAQ, should be closed by casting close votes. Common reasons for question closure are:
- You asked a question that was asked before
- You asked a question that is off-topic
Typically, though, most self-closed questions are either duplicates of another post (that you didn't just see), or they can't be reproduced because they were fixed.
Remember, closing as a duplicate isn't a punishment -- it acts as a signpost to guide new users to other questions that are far more likely to help them solve their problem. Similarly, closing your own question as off-topic when needed allows us to focus our efforts on solving other problems on-site, wherever they exist.