Carl Zeiss Macro-Planar T 100mm f/2.8

Pros Excellent picture quality
Cons Requires very accurate manual focusing

My personal copy of this outstanding lens had a tiny ding on the focus ring which resulted in a acceptable sum paid, even in times of ludicrous ebay prices.
IQ basically is outstanding with a 3D-like touch, impressive resolution & sharpness right from open aperture.
In Macro-mode, accurate focusing requires either a precise adapter with AF-confirm, a split-screen brightscreen or live view.
If focused correctly, results will be as perfect as it gets.
Sold mine for a EF Voigtländer APO-Lanthar SL 125mm f/2.5 - still not shure if that was an improvement.