Things we did in our house:
-Two showerheads in large master shower, one standard and one with handle on hose.
-Wash basin in the garage. I use this ALL.THE.TIME.
-Switched outlet in the front eaves, easy Christmas lights if that's your thing.
-2X 220V outlets in garage, one for compressor one for welder.
-Pre-wire for sprinkler and/or pool pumps.
-Skipped the home phone line.
-Concrete parking slab on side for boat or extra cars
-Outlet and cable mounted high on back porch wall
-Epoxy flooring (so far so good) in garage, I used EpoxyCoat.
-Defined walkable attic area for storage, with a pull-down ladder. I've sheeted one area in with OSB over the studs, and wish I had done a 2nd area. The wiring up there isn't routed in a way to make that easy.
-Pre-wired for surround sound in main area and 2nd circuit speakers to back porch for music (though I missed where these should have been)
-Take pictures of where all the studs are, and electrical routing
Things I wish we had done:
-Heater combo in the bathroom vents, requires heavier circuit
-More exterior lighting, to side (boat storage/working) and back (dog relief)
-Wired in for thermostatic attic fan (South Florida specific)
-Double-checked the attic convection net free area (vents are way under-sized), I have a bunch of info in a corner-carvers thread if you are interested.
-Upgrade the switches and outlet covers, this is kinda expensive to re-do
-Upgrade the roof (builder wanted crazy prices for this, like more than a new instaled roof just for the upgrade in material)
-Exterior back porch showerhead (I just use the hose)
-Specify a double-thick beam area (or build in a metal I-beam) on top of the garage for hoisting heavy things (like boat motors or motorcycles)
Edit: Sorry this forum lost the formatting when I posted. Custom forum software still sucks.