Olympus OM 135 f2.8
I have quite a few of these 135mm lenses, all manual focus of course, because they produce some great images with the new digital cameras. Good light is normally always a requirement if shooting hand-held an it is an equivalent of a 270mm in 35mm terms. These were produced as a f2.8 of f3.5 lenses. Personally I prefer the f3.5 variants as they are much smaller and easier to handle. Not much slower than the f2.8 lenses but the weight difference IS very noticeable. Another great feature of these lenses is the built in hood which just slides out when required.