Have built 2:
Mud room with built in cabinets and hangers. Cannot be big enough… ever!
Tankless water on each side of house. I hate waiting for hot water.
Several drawers in lower cabinets especially corners. I did drawers both sides of oven and corners.
Larger front and back porch than you think you need.
Hanging rod built between cabinets in laundry also sink
Pocket door to hallway (can close off if kids, dogs, etc…)
Larger saferoom than you think you need
I think if I built another I would use the marble slab (think hotels) vs tile shower. Pain into keep the grout clean in large shower
Heated tile floor in baths
If your forever home then spray foam. If not the pay back is too long.
Gas stove needs to have the griddle burner in middle
Fiberglass exterior doors. Real wood is A LOT of upkeep.
Insulated garage doors (3 layer, so insulation is not exposed).
Built in shoe rack in bedroom closets.
Accommodations for hanging tvs (outlet up high)
Don’t skimp on windows!
I like brick accents inside (think entry ways/large door openings.
Office
Entry door to garage. Not just garage doors.
Everyone loves our hidden pantry. (Looks like a large cabinet)
Plenty of storage closets, entry coat closet

We chose a floor plan close to what we wanted online and then had an architect draw it on his software. Much easier to start smaller than the square footage you want. Makes for easy changes with software.

Dont forget a place to store your corn

Doc, it sounds like you actually need a couple of different things.
First is the actual floor plan, then a list of building specs and last all the specialty items that have been mentioned by some.
The floor plan would basically be just that, the actual layout of the rooms and spaces with sizes.
The building specs would be a list of how you want it to be made of ie. construction materials plus things like roof type (gable or hip) interior and exterior finishes, locations of certain, insulation, stuff like that.
Last list would be appliances, cabinets and countertops, colors, how closets and other spaces are laid out.
Once you have this, any reputable architect could do the floor plan, elevations and construction specs drawings for you.

Lots of good things mentioned here. I am with showout on the entry door to garage. I cannot tell you how many times I have closed the garage just to realize I have forgotten my drink, phone, etc and an entry door would be nice to have instead of opening/closing the garage. I feel like one of the biggest things you need to do when building is to use the best quality paint(interior and exterior) there is. You will never regret having good quality paint and to repaint the house in several years due to low quality paint will cost a hell of a lot more than just using good paint up front.

Good point. My father was a high end home builder , he always insisted on hiring the absolute best painters. He always said folks building have it all wrong when it come to painting. Many folks think they can paint or have a BIL that will do the painting. You want a high end painter on a new construction . Good painters use good paint and a good painter makes everyone else's work look good.

Should be about $185/square foot

I draw plans for people every now and then. Find something similar to what you like exterior wise. Go get a graph paper pad and make each square so many feet and start laying it out. So many people scratch something out and try to fit the hilton into a shoe box and it just don't add up. Make your bedroom's a little bigger than you think you need.

A lot of good ideas Doc, here’s some more.
Larger and more windows in living area, view and light.
36” pocket doors.
Plantation swings on porch and ceiling fans.
Thermostat controlled attic fan.
In the shop, on demand water heater, floor sloped to drain in center of bay.
Insulate it and more plugs than you think you’ll need.

Don't over look the laundry room. We love the extra space in ours. Most of them are cramped spaces. Make sure the garage can hold a full sized pickup/SUV with plenty of room to walk around it. If septic, look in to a aerobic system. No leach fields. Depends on your lot size.

From slab to CO, what most of y'all are describing (2x6 exterior walls R19 insulation, manabloc plumbing manifold, nice but moderate interior finishes, and a grassed front yard) the vertical construction cost (including slab) right now is running $134 to $145/SF (that is the "dead cost" of construction) The $10 variation in cost is dependent on the lot topo and foundation work required. Mono on the low side, block work and fill on the high. Those numbers represent true cost of construction with no builder profit or overhead. Lumber has come down some in the last year but everything else has gone up, block, brick, vinyl, Hardi, concrete, labor, pipe, shingles, sheetrock, fixtures, cabinets, paint, etc. If lumber was still up where it was, you could add another $8-$10/ft to the dead cost above, on a 2,400 SF house. Six years ago, same house could've been built for $90-95/SF. It's ridiculous, I know, but I get price increase notifications from suppliers and subs every single week, it's simply not stopping or slowing down.

Find a base floor plan that you like, make a list of what you want to change or add, let a draftsman work everything up, meet with your builder and let him go through the plans and make suggestions to help you value engineer the house based on your preliminary drawings. Then go back and have the draftsman revise the plans incorporating the agreed upon changes, then get an engineer to stamp and seal the plans (most good draftsman, and builders, have a agreement with a local engineer). Including your builder in the design phase will normally save you thousands. If you don't build, you dont realize that very minor changes in design and materials, can save big bucks while still achieving the look and house that you want.

If building on a slab with pex piping we had our lines cased in 2in PVC that way if there ever is a leak or burst pipe I can just cut off from the outside and pull through the PVC sleeve. I had them put a sweeping 90 on the upside so I can push new pex through easier. That way I wont have to bust a slab to fix a leak.