1. 35mm f/2.0 Summicron - Small, easiest to use and carry around and my favorite focal length.
2. 50mm f/1.4 Summilux ASPH - THE lens, no getting around it though
3. 90mm f/2.0 Summicron Pre-ASPH - Great for details and portraits absolutely love it, and after focus calibration with my M9 it is stupid good.
Leica 90mm f/2 Summicron, initial thoughts | Brian Hirschfeld Photography
I also have the 24mm f/1.4 Summilux which was given to me as a gift, it gets a walk around every now and then or when I know I will be wanting wide angle. It is currently with me in Amsterdam and getting a workout on the M9 Monochrom. To me, it is an "ultra-wide". Anyone think its worth getting the external viewfinder for this lens?
The lens I absolutely regret selling is the 35mm Summarit, absolutely wonderful lens and my copy was totally perfect in every way. I had it since my M8 and then sold it when I got my 50mm Summilux because it was already redundant with the 35mm Summicron.
50mm Summarit is a tolerable lens, no complaints but nothing exceptional about it to me. I sold it along with the 35mm Summarit when I got the 50mm Summilux because it was also redundant at this point. I owned the 50mm Summarit for the shortest time and was probably the lens I have liked least among all the lenses I have owned.
Rented the 35mm Summilux for fun, and didn't find it to be a terribly big IQ improvement over the 35mm Summicron to me so I saw no reason to upgrade to it.
Considering getting the 90mm ASPH APO, and either the 135mm f4 or the 135mm APO. The 90 APO ASPH would replace the Pre-ASPH and the 135mm would be for special situations.