efix
RF user by conviction
Not so wide on an M8. But my 21 Elmarit is too heavy so a 28 sits on my M8 for "wide" shots. Maybe a CV 15 would be perfect in wideness and weight.
Yes to the 15mm Heliar if you want to go REALLY wide (20mm-equivalent). Note, though, that you will need to code it if you're going to use it with a UV/IR filter. And even when coded, tinted corners may appear. But that a general problem with wide angles on the M8.
Another vote for a 28mm as your walkaround lens. Framelines are perfect, and equivalent field of view of a 37mm lens makes it a great allrounder.
My flickr set from the 28/2.8 Biogon
My flickr set from the 15/4.5 Heliar