My favourite lens is my Sigma 400mm F5.6 Apo/Macro HSM lens which I've used to shoot everything from damselflies (
http://www.worldphotographyforum.com...7810&ppuser=43) to Mont Blanc (
http://www.worldphotographyforum.com...7810&ppuser=43). I can't understand why Sigma don't still make this lens - look how many times people have bemoaned the fact that the Canon 400mm F5.6 doesn't focus as close as that company's 100-400mm zoom lens, yet there are still lots of the prime lenses around which are potential lost sales for Sigma.
The lens I dream of getting probably isn't available yet, as I would like to carry around something smaller and lighter such as a micro 4/3rds system camera but as far as I know there isn't anything that can match my 400mm in both image quality and long-range 'macro' capabilities. When you add in the HSM 'silent' focus and full-time manual-focus over-ride via a generous-size focus ring, etc., there are just too many compromises to take into account, so I'll just have to dream on for the time being...