Originally posted by StiffLegged I should like a 12-24mm, but the 20-40 Limited (in black) would be a lovely bit of highly flare-resistant glass for a walkabout wonder.
I've got both (and the HD-DA 15 Ltd). The 12-24 is a good lens, and there is often no substitute for its width, but I love the 15 + 20-40 combination as a compact, portable, WR, HD pair with that Limited magic.
I don't see that you can have just one dream lens unless you do just one kind of photography. The 15, 20-40, FA 77 and DFA 100 macro are all dream lenses for what they do.
For wildlife my dream lens doesn't exist in K-mount: a lens with more reach and better AF than the DA*300, and less weight and cost than the DFA 150-450, but with comparable IQ.