When pinholes are used for extreme panoramic photography, the "squint" that NedL mentions above is exaggerated. In theory an elliptical pinhole with the major axis horizontal should reduce astigmatism and increase exposure at the ends of the image with a loss of sharpness in the center. I haven't wrestled with the problem of making elliptical pinholes small enough for compact panoramic cameras to test this. However, tilting the pinhole backwards when using the equivalent of a rising front in a wide angle "tall building" camera is effective in improving sharpness near the top of the building. It also makes exposure more even over the entire image. This is one practical application of a pinhole that is effectively elliptical.