I'd add for telephoto that the two Summarits (75 and 90) are both spectacular. I sold the 75 to fund my 24/3.8 Elmar ASPH (another FANTASTIC lens fairly low on the Leica price chart), but will buy again. The 90 Summarit is everything you could want in a portrait lens. Sharp, beautiful bokeh and much smaller and lighter than the slightly-faster Summicrons. Oh, and its cheap.
My curent lens lineup is as follows.
Leica 24mm f/3.8 Elmar ASPH - Incredibly sharp from corner to corner, even wide-open. Minimal distortion. A bit slow, but the M Monochrom is quite good even at ISO 5000.
Leica 35mm f/2.5 Summarit - While a 35mm lens at f/2.5 won't completely blur much of anything, the bokeh of this lens is about the smoothest of anything I own. Extremely flare-resistant as well. Has some moderate barrel distortion, but nothing thats ever bothered me (I don't shoot many brick walls).
Leica 50mm f/2 Summicron (current version) - What can I say? Classic rendering, modern sharpness, no noticeable distortion. Bokeh is exceptional, sometimes, but is also often quite caffeinated. If I could only keep one lens, this would be it. One of my favorite aspects is that it renders out-of-focus objects smoothly in the foreground, which many lenses just don't do.
Leica 5cm f/2 Summitar (1949 coated, 10-blade) - Don't know yet. Just bought it, currently at Sherry Krauter for full CLA.
Carl Zeiss 50mm f/1.5 C Sonnar ZM - Fantastic people lens, but also tack-sharp when stopped down to f/5.6 or f/8. This is basically two lenses in one, but has wicked focus shift from f/2 through f/4. I use this wide-open most of the time though sometimes at f/8. Basically this is a lens with a two or three position aperture, but at those two or three apertures (especially wide-open) it is magic. Mine is optimized for close focusing wide-open, stopped down depth of field covers the focus shift, which is only a problem between f/2 and f/4 where I simply don't shoot this lens.
Carl Zeiss Jena 5cm f/1.5 Sonnar (1937 uncoated) - Everything above about the modern ZM version applies, but this one is lower contrast and will flare if you don't use the hood. I always shoot this through a multicoated filter (yellow or orange most of the time).
Leica 90mm f/2.5 Summarit - My least used lens, but the one that gives me the highest percentage of keepers. Focus is spot-on with my M Monochrom and the bokeh is just delicious. Very resistant to flare and sharp, even wide-open.