A lot depends on what you want to spend. I'll share some things that I like in the house we built that was around $250k. If you are a building a $800k house, I would say just add gold to everything I noted below.
We built two years ago and one of the main things I wish we had did differently is make the laundry room larger. It is the entrance to the garage from the kitchen and when the kids are trying to get their shoes on in the morning to leave or coming home with everybody it is a cluster. We put roll-out trays in the larger base cabinets and I like those. I also have a small 9" cabinet next to the oven that is used for cookie trays. Think about where your trash can will go and consider if you can give up a base cabinet to use for a roll-out trash can. Also, soft close cabinet drawers and doors are very nice. Especially with kids.
We have a wetbar in the basement and we decided to put a full size fridge down there instead of an under the counter fridge. The extra fridge space when you are having people over is great. Or when you are smoking and need a spot to keep lots of rubbed meat overnight.
I am super paranoid about water so we had them put in a water-powered back-up pump. If the electricity goes out, it will work as long as you still have municipal water. With these, you don't have to worry about checking the battery. I'm glad we did this, because I hear the sump pump running all the time. I kinda wish I would have added a second sump pump pit that left the house through different pipes.
We also added a back-flow valve to the sewer line so you don't have to worry about sewer back-ups.
We also added a patio slab at the bottom of the deck stairs. I like having the deck and the patio. I wish I would have added another light outside the patio door, though. They only put one out there and I wish there was one on both sides of the deck.
I would also suggest looking for home websites with message boards. Lots of threads like this with other people building or have built and I remember getting ideas from those sites.
Make sure to leave room in the bedroom for a sex swing.