This feature request was declined by the community for a good reason – on a regular SE site, posting controversial questions or answers should usually not be considered positive behavior.
On Area51, however, I consider controversial questions (i.e. many on-topic and many off-topic votes) highly important, because they pretty much draw the borderline around the proposed site.
Having many trivially on-topic questions and many obviously off-topic questions is all good and well, but might not really help define the site. The controversial questions, on the other hand, clearly show where certain decisions and definitions have to be made for the site not to grow out of hand.
Thus I suggest a badge for posting a question that has many (quantity to be determined) on-topic and off-topic votes. Name suggestions are obviously encouraged.