I often prefer a 5:4 aspect ratio over 4:3 or 3:2 for my photos. 4x5 is available as a crop ratio, but I'd love it if 5:4 was available as an aspect ratio when shooting so that I could compose my photos as intended without having to crop them later.
It's been mentioned here before, but nothing has been done yet, so I'm bumping the idea again. We need to be able to shoot in the 4:5 aspect ratio (among others) for pre-visualizing Instagram verticals. Please!