Problem: The only tool to search Wikipedia currently is a simple direct keyword search which looks for literal query matches. If any information is needed, the only way to find it would be to try searching specific keywords or phrases which must match perfectly with the information one is trying to find. Wikipedia is filled with so much information, yet so much of it is hard to find because of this. Even if one knows what article contains the information they seek, the only way to find specific information would be to use keyword matching search (which would make specific information hard to find, especially in long articles).
Proposed solution: The proposed solution would be a Wikipedia semantic search which can help users find information using natural language queries. This means that one could enter a question like "What is the deepest point of the ocean?", and they would be directed to the section of the Wikipedia article about the Mariana Trench which explains this fact. This is not only a possibility, but is already used by many search engines like Google (which has many more pages to index than just Wikipedia). This would have a tremendous impact on the future of free knowledge as it would make finding information significantly easier.
Who would benefit: The group that would benefit most would be those who are looking for specific information or to have a question of theirs answered.
More comments: I have briefly worked on a project independently which allowed for semantic search within a Wikipedia article (i.e. if the user wanted to know when Tiger Woods began golfing, they would choose the Tiger Woods Wikipedia page and search something like, "When did Tiger Woods start golfing?"). While this is on a smaller scale, it can be extended to search all of Wikipedia. Further, along with readers benefitting from this tool, editors who are looking to make contributions to specific articles that contain topics they are familiar with can use this tool to find these articles (and sections within those articles) to which they can contribute.