Room layout
So I’ve had this idea that I’d like to rearrange my room. I’d like to try a bunch of different layouts without actually having to move all the heavy furniture. My mum loves doing this sort of thing, and she uses special square grid paper representing the room, and little cutouts representing the bits of furniture. That’s OK, but there would be a lot of advantages to doing this sort of thing with a computer. The Sims is actually pretty good for this sort of thing - you have enough flexibility to make rooms of interesting shapes, and a large-ish selection of furniture. Then you can more-or-less fly through the room you’ve made and see how it looks.
But I think software specifically designed for it could do this better. You could use real dimensions on the walls and furniture, place items at off-90° angles, save layouts, get architecty-looking printouts, etc. I don’t think I’m about to write it, but it would be very useful.