On a serious note ... I've always wanted an algorithm to rank images by sharpness/focus and wondered whether that was doable.
That's fairly easy, actually. All that is necessary is to evaluate the amount of high-spatial-frequency information present in the image data and calculate a score for the image, then sort accordingly. The only real trick would be separating noise from actual image data, or high-ISO images might score a false positive for focus. You'd probably have to segregate images by ISO (only compare results with other images shot at same ISO setting) for best results.
