If you have a walk in linen, make sure there is broom/mop storage and not just shelves.
Dimmers on the bedroom lights,
Plenty of drawers in the kitchen, I wish I had more drawers and less cupboards so I wouldnt 'lose' things in there.
This might not be for everyone, but I wish I had a robinhood (ironing board on the wall) in the laundry because I hate setting up and down the ironing board and iron.
Proper positioning of power points to make best use of them without them either being obstructed my furniture, or so far away you need an extension lead.
Extra tap points outside,
Data/Foxtel points in multiple rooms.
There is probably more, but I can't think of it.