One I liked was the Zeiss Opton f2/85mm..
Perfect at wide open to F4 for Potraits. I used an Amedeo adapter with a Contax RF copy.
There are LTM copies out there from Zeiss Jena.
There was something about that Opton time that was special and I think worth the pursuit.
In the US Many GI's came home with Zeiss Camera sets.
The 2/85mm was a tough lens to use on the Contax ii and iii rangefinders.
One had to view focus through the VF and then compose through a finder. At F2 it was hard to hit focus and I think folks thought the lens soft.
As a result many of the lens sat in drawers and are now in pristine condition.
They are gorgeous lenses for the Digital Leica RF's and film alike.
The Nikkor f2/85 LTM has a similar signature and is less expensive as it's more abundant. The Zeiss is special though and worth pursuing.
I used mine on the RD1 and M8 and film as when I owned it he M9 was not available.
Had to sell during a dark period.
There is a 3 shot Bokeh sampling
here f2,4,8.
Below are some old digital files I have on Flickr
Rd1
Opton285 4 by
Adnan W, on Flickr
Opton285 5 by
Adnan W, on Flickr
M8
One or the other. by
Adnan W, on Flickr
Opton285 13 by
Adnan W, on Flickr
And here is the lens and adapter on the RD1. I would easily like to buy it back!!
Opton285 6 by
Adnan W, on Flickr
Opton285 7 by
Adnan W, on Flickr