Electricity! Thankfully, my coop isn't that far that I can't run a long extension cord out there. I have a solar unit that can run a few things (right now it runs two small fans and a light), but full on electricity would be soooooo much better.
And water! I have a small flock and a small coop in a relatively small yard, but a dedicated water source would be great for all sorts of reasons. With a utility sink!
And an auto door so I can sleep in a bit on occasion.
And air conditioning, although I may add this soon. It's 107° right now, and inspite of all the frozen water bottles, fans, cold eats, etc, it's still hot as Hades out there.