I've got a mattress pump that runs on 4 D cells, although I use D to 3AA adapters in it and load it with rechargeable AA NiMH cells whenever we go camping.I just bought D cells to replace the ones in my old school Maglites. My auto cat feeder uses D cells also.
Also, there was some talk a while back about which batteries sell out the fastest in an emergency (like when hurricane is approaching). I can't recall now which one it was, but probably AA since it's the most popular. Sometimes it's good to have one or two flashlights in your arsenal that take an odd size battery that nobody else wants to buy.