Flash
I don’t have a problem with Flash when used appropriately, but many sites that are ENTIRELY Flash based create an excruciating user experience.
Take for example this wallpaper site I found this morning when Pixelgirl didn’t have anything fresh. It’s not just that the animation makes the process so slow, but that every time you change authors to look at another 4-5 images, the animation runs again. I looked at 3 pages, and then gave up.
Square peg round hole. I don’t think a desktop image site is the best place to showcase your Flash skills.