First answer that comes to mind is, of course, 'all of them'.
Though that's not got any nuance and probably depends on if you're after preservation, making something more accessible, or just data hoarding for the sake of data hoarding.
Given the current state of things in the world, I'd say any sort of scientific, health-related, or similar type of content would be where I'd immediately assume the greatest need is.
Edit: Anything relating to trans healthcare, in particular. As well as anything even remotely non-straight.