Canon MP-E 65mm Macro
A fairly specialist macro lens, this starts its magnification where many macro lenses finish, at 1:1... it then extends to a remarkeable 5:1.
Its not really useful for anything larger than a wristwatch... but then it excels in the world of tiny unseen details, filling the frame with textures impercepteable to the eye.
Its tricky to use, the barrel is used to set the scale of the magnification required and then focus is best achieved by moving the camera in relation to the subject... so elaborate sliding plates are needed, depending on the size of camera. Whereas in the world of stills most would use it combined with a flash... in the world of motion it requires a fair bit of lighting. When at full extension (5:1) the light loss renders the f2.8 aperture more like an f11. So if you prefered a deeper stop, say f8, you would be looking at f32 levels of light.