70-200 F2.8. So far have Sigma 70-300 APO and Bigma, so that covers the range, but still it is a dream.
Another would be 100mm WR. Though while I don't have it, still doubt between it and Sigma 105mm Macro (especially, as one 105mm is for sale on KEH now, for Pentax mount... but because K-30 shown the aperture, had to buy KP, and no money for the lens... again).
Anyway, these two were my dream lenses always.
---------- Post added 2018-06-15 at 22:24 ----------
Originally posted by photoptimist Sigma 50-500: love the idea of the 10X zoom range, love the idea of getting to 500 mm on FF, but..... the bulk and the price have always stopped me from clicking "buy" button.
Oh yeah, it has bulk and weight... camera is only an attachment to it (I got it second hand for good price)