The 40 mm focal length isn't as common as 50 or 35 mm lenses. It is neither considered wide-angle as the latter, or 'standard' as the former. For me, the focal length is just wide enough, because depending on how you move when composing, it lends itself to a varied use.
Minolta Hi-Matic C
This is a favourite camera that I've mentioned before. It may be the most complete viewfinder camera that I've encountered, in the way that the design and features are honed to help the user to make the correctly exposed photograph.
Below are some photographs made with the Mamiya Family camera's 40 mm lens. I love the swirl! The camera is a joy to use. If I didn't already own an SLR or two that I use more I would have kept it, for its small size and ease of use.
There's a dragonfly!
Pentax 40 mm
Finally, here are some photos made with the 40 mm pancake lens mounted on my Chinon CA-4 SLR.