Plenty of coat hanging space - beside the door for daily coats/boots/bags and storage for the rain/wind/warmer days/going to sea full protection etc options.
We have a drawer for shoes in the hall under the stairs - genius!
Utility room to get to back garden complete with big sink, tap to rinse boots etc, drain in centre of floor, laundry facilities and plenty of storage for cleaning things, paper products, laundry baskets/pegs etc behind closed doors. Probably with a Nora Maid (? wooden slats on a pulley system) from the ceiling to hang clothes to finish drying.
Walk in pantry with a cold shelf, food storage and also "best" (occasional use) crockery/cutlery/serving platters/glasses. And a space for linens - tablecloths, napkins etc - to be able to do seasonal table dressing. I long for a decent basement for food storage and wine stocks, but once there is a space there with not too much by way of temperature fluctuations, I'd be happy.
A craft room. With LOADS of storage and a LARGE work table. LOTS of natural light and directional working light for after dark. Mix of shelves and bins. Room for lots of tools, and to have projects left out undisturbed overnight. And also a comfy chair to sit and knit or hand sew the end of something. And speakers/music centre.
Space for instruments - I have no piano since I left my DPs house, and my guitar rarely appears from the back of a wardrobe for fear of damage. That would be in a library type room, with a good music system and speakers, and also lots and lots of bookshelves well filled, and a few comfy chairs to read or listen to music.
2 sinks in the bathroom would be good. Proper rails for towels, preferably heated. And a proper storage unit for the spare shampoo bottle etc (so you're not running into the bedroom dripping halfway through washing it!). Well ventilated bathroom as well.
Plenty of insulation, lots of good windows to let lots of light in but not heat out/in (keeping cool in summer and warm in winter). Underfloor heating would be good. And a wooden stove for heat, perhaps with a back boiler to take any excess heat and put it to good use. Solar panels for hot water or electricity/battery charging.
Good cooker (5 ring, double oven) and fridge (large capacity). Probably a chest freezer or good upright freezer for longer term storage as well as a small everyday one (I like an American fridge/freezer, but would need more freezing space for veggie gluts, batch cooking and the like).
Tranquil bedroom.
Which means a separate dressing room with loads of organized clothes storage and dressing table with good lighting (natural and artificial) and lots of sockets.
I can't think of other stuff right now.
I know there's more. But most of that will never happen. Cos we'll never build our own, and we can't fit a lot of that in a suburban semi-d.