Johanna Rothman has an intriguing idea for a screening question: ask for a paragraph detailing the candidate's most significant accomplishment in the cover letter.
In my experience, this would have immediately eliminated nearly every bad candidate I ever interviewed . Instead, we had to ask the question in the interview and find out how unqualified the applicant was. It was painful to find out how little people had accomplished to generate the barely-adequate resume they supplied. It also would have established some excitement around a candidate who answered the question well and led to follow-up questions at the actual interview.