I am constantly using the Rotate to Line feature. In particular, I receive a lot of images that originate as quick snapshots of business cards and similar material.
Often, the snapshot was taken at an angle, so the rectangular object appears "in perspective" as a trapezoid.
It would be wonderful to have a tool (like the Rotate to Line tool) that would allow me to define the trapezoid and would then stretch the image to make that portion of the image rectangular. I think that drawing two lines, one for each non-orthoganal side of the trapezoidal area, would be very useful. A more advanced feature that allowed drawing a rectangle around the area of interest and then dragging corners would be even more powerful.