The Canon LTF 19mm F3.5 FL is difficult to find, but similar to, and 1/3 to 1/2 the price of, the Leitz Super Angulon. I had a nice one until recently, and it was entirely satisfactory for my many uses. Worked great on my Leicas too, and has a lower-contrast "look" to it. If you get the FL model, you will also need the Canon Adapter B to get you to LTM.
I've also owned the 21mm Voigtlander Skopar, and it's contrastier (as one would expect) and sharper as well. A bit too clinical, for my tastes, so I sold it. Was particularly fantastic on the M5, I remember.
Sony Nex-3/Minolta SRT's/SRM's & XK/Hasselblad's/Plaubel Makina III & Makiflexes/Sinar Norma's
Some of my older pix: http://www.flickr.com/photos/1813448...n/photostream/
Some of my even older pix: http://hassydan.tripod.com/
"There is nothing worse than a sharp photo of a fuzzy concept" -- W. Eugene Smith
"Cars and Guns have gotten me in trouble. Cameras haven't" -- Jim Marshall