In bright sunlight, our usual reaction is to eagerly stop down for increased depth of field. But the combination of vignetting and shallow depth of field can focus attention. This is an area I’m keen on exploring at f/0.95 and f/1.4 with lenses like the Leica 50/0.95 Noctilux-M and the Nikon 24mm f/1.4.
Anyone with an f/1.4 or faster lens might want to consider adding a neutral density filter to their repertoire. For an f/1.4 lens, a 2-stop filter is a good choice for most shooting but might not be enough for very bright scenes (eg snow). A polarizer can also work because it cuts 1.3 - 2 stops. A 3-stop, 6-stop or even 10-stop filter can all be useful. There are also variable ND filters which are essentially dual polarizers, but they are more expensive, and can be prone to other artifacts, so I stick to regular ND filters.
ND filters also allow blur of moving parts of the image, such as moving water or people (when a long enough exposure is used).
This shot is at f/0.95. I took it as a test shot, but I like the simple result; the combination of color, vignetting and very shallow depth of field make it visually interesting, perhaps also because those two effects are at odds with what most daylight photos look like. The shot almost looks like a miniature, similar to the effect possible with a tilt lens.
Note to Leica: when servicing cameras, restore user settings so that the camera is not set to stinkin' JPEG when user had it set for uncompressed RAW.
Also at f/0.95, the shallow depth of field and vignetting really pull the eye into the center.