I personally searched for and couldn't find an app that gathered various random generation tools, like the ones on random.org (integer sequences and sets, dice, list shuffle...)
Other than that banking, transport, government apps are (almost) never on fdroid, but that's not something a weekend project can fix :)
and I was wondering "which apps do you think are missing" ? (it can be games or even very specific needs)
as I think lot of people are like me here, we would like to hack on some "weekend project" but we lack creativity.