Before you begin the build, buy two safes for the house - one for the master bedroom, either a floor or a wall safe, and think about where they should go... I put the wall safe in the wife's walk-in closet, and the big safe (Is also a Firesafe) in the most distant place from any entry, on the lower level, bolted to the foundation, in a room with doors too small to get it through.
Think about home automation: The Levitton/X-10 system requires a separate ground conductor to each gangbox. It allows things like "All lights on" when you approach the house, or when you want to allow quick exit, and will do things like set the lighting levels, turn off the alarm system, open the gate, and turn up the heat and hot water, and turn on the water, either by wireless remote when you near home, by telephone and/or by remote access to your control computer.
Give a lot of thought to the siting of the home relative to the Morning Sunrises, or prevailing winds, or views, or Sunsets, or when you approach the house it presents itself to best advantage, or hiding from prying eyes - try to capture as many of these features as you can - this is the province of the Architect, but you must lead. The way our house faces the Morning Sunrises is one of our favorite features of our present house - it provides a natural alarm clock, and the house warms up instantly most mornings - a good feature here in the Northwest. Then in the afternoons, it provides shade, as the opposite side of the house is facing 200 ft tall evergreens.
I wish I had installed the radiant floor heat, with room-by-room zoning. It is dead silent!
If I get/design/build another house, I will have "Tankless" gas hot water heaters, and built-in Electrolux vacuuming systems.
Think about siting/sound insulation for an Emergency (Natural Gas, if available) generator system just outside/near your main power distribution.
30 Amp outlets in the Garage, and outside the Garage, and maybe on the opposite side of the house exterior, along with a water faucet, and an air outlet/hose at the outside of the Garage - Air compressor just outside the garage is better than inside, but gets better maintenance and lasts longer inside.
Wire in your computer network, as it makes your info more private.
Each room in this house has multiple landline wiring, and cable and security wiring, and each circuit is already wired redundantly. 20 Amp outlets in every room, and never more than 10 feet between one and the next.
Wiring is such a headache after the fact - I am leaning towards either commercial raceways for power and communications wiring, or multiple conduits within each room for my future house, if I ever do it again.
I wish I had thought to make all the services machinery remote - outside, or in an outbuilding - refrigeration and airconditioning compressors are noisy, and so is the hot water exhaust blower, the heating plant ventilation blower, etc. Then the house would be blissfully dead quiet.
I like zoning each room's lighting and power outlets separately - two breakers for each room/zone.
In Handicap accessible suite, include a walk-in tub.
Sorry, for security purposes I won't show you my house, but I favor open design Kitchens that adjoin the Living Room, or the Den/Family room, as when you are entertaining, the KITCHEN is where the party is really happening. Lots of countertop/stools outboard of the counters, and convenience features opening/facing inboard.
The most expensive room in the house, the Kitchen is where I really like to go nuts - pull-out refrigerator drawers, lighting, island features like cutting board surfaces, sinks, gas cooktop with vent hood and lighting. Cool features like a dumbwaiter to the Wine Cellar below (we made ours big enough to handle the laundry also, as our Laundry is on lower level), a walk-in pantry, and a wine refrigerator facing the Great Room are nice too. I have 220v wiring in a couple places in my kitchen here in the U.S., because the British have got the electric teapot and Dualit toasters figured out - there is nothing better IMHO. 220 is great for the ovens, and a fryer, if you want one. Whichever of you is the cook should give a squint at all the wonderful oven technologies: Radiant, (Forced)Convection, Microwave, and so on - we wish on one of each!!!
We designed the house so that the Wine Cellar is beneath the Kitchen, and that is where the Kitchen fire supression system tanks and valves are - that way, if there is a house fire, the tanks will discharge to help save the wine and the Main Firesafe.
Hope this helps.