Cat 6, Cat 3 and Coax to every room. Cat 6 + power to a few closets for WiFi APs.
Structured wiring to a central ethernet/phone/TV distribution hub with media server, UPS, etc...
- The above can cost thousands of dollars if done professionally. My brother-in-law did it himself (before his house was drywalled) for a few hundred dollars.
Solotubes in the bathrooms (basically mini-skylights that collect enough light at night to act as a nightlight)
Hookup for solar - the tech isn't *quite* there yet.
Hookup for garage EV charger - see above.
Multiple passthroughs for wires going outside - for future expansion (ham radio antennas, sprinkler systems, whatever)
If you're really into gardening, a hookup for an outdoor sink (with warm water) is *really* nice.
A properly wired OTA TV/FM antenna - for cord cutting.
Depending on the size of the house - multiple thermostats.
IP thermostat with integrated humidistat to control the humidifier. I like the Nest.
An attic fan with a nice controller - won't live without one of these now - we can go for most of spring without A/C by just using the fan.
Metal roof - recommended by a roofer friend who has them on his house - if properly installed they will last practically forever.
If you don't want a security system, at least run some LV 2-wire to each window and door so you can add one later if you change your mind later.
Also run wiring for connected, powered fire alarms. At the very least - one in each bedroom, one in the kitchen, one in every stairwell and one in the furnace room.
Ideas from a local builder:
2x6 framing - allows for more insulation and is more durable.
16" poured reinforced concrete foundation - recommended by structural engineers as ideal for residential construction.
Remember this - building to code is like getting a C on a report card - you're doing the bare minimum to make sure the house won't fall apart, flood or catch fire.