Contax G2 (or G1) with Carl Zeiss 24mm or even a 21mm.
That's compact. Optical quality is the top of the top of the top. Not a toy. I don't know if it fits your definition of "pocketable". It fits in a bumbag with a couple of lenses, or more.
Ricoh R1, if you don't want to spend a fortune. 30mm, 30mm panoramic, and 24mm panoramic. But the panorama mask is easily disabled if you want full-frame 24mm. And it is one of the most "pocketable" cameras ever made.
The XA4 has a 28mm, f/3.5 lens. Pocketable like the XA but scale focus instead of rangefinder and auto exposure instead of aperture priority. Still, decent lens given the tiny package.
The other cameras listed so far certainly beat it in quality but XA4s are very pocketable and relatively cheap - compared to the Natura, Contax and Ricoh - if you can find one.
The Ricoh GR1 family with the 28mm lens probably fits the bill. It's very slim and certainly pocketable. Has some nice functions too such as focus lock, 'snap' mode which eliminates shutter lag and exposure compensation. It also has a very nice lens. There's also a rarer 21mm version which sells for big money.
A Konica TC or TC-X with the later compact 24/2.8 Hexanon would be more versatile than any fixed-lens camera. Greg Weber should be a good source for both.
i did a bit of research.. the Natura, and Ricoh GR1/GR21 seem a bit overpriced to me.
The Ricoh R1 seems to be more reasonably priced going by recent sales.
The Contax, though high priced gives you alot of value for the money. But I question the pocketability.. Just how much smaller is it compared to a compact SLR like the Pentax ME or olympus OM2? Coat pocketable?
Regarding the XA4.. Thanks for example pics. They look great. Not quite as wide as I was hoping for but it looks like it may be my best choice.