Xanadu, if you consider “stately pleasure-dome” as being synonymous with “house,” which I and all right-thinking people certainly do.
The Four-Story Mistake.
Hill House. The Halloween parties would be spectacular.
When I was a kid, I was going to make it my life long ambition to live in the Wichester Mystery House.
Now, I’ll go with the Playboy Manchine. Just because.
I’ll go with Castle Dracula from Castlevania: Symphony of the Night. I’d never get bored exploring that place over and over again. 
The Truebas’ home in The House of the Spirits.
Snug Harbor, from Robert A. Heinlein’s The Number of the Beast.
:: crossing fingers that I beat What Exit? to the punch ::
Awww . . . with the cupola!
Monticello, but mainly for the wallpaper.
Other than that, I’d pick the magical mansion my dad looked at for a family dwelling in the center of Mayville, NY. I call it a mansion because although it looks like your typical square Northern house, it is on a medium-sized plot with an orchard and used to have out buildings.
I call it magical because although it looks like it has 2 main floors, a basement and an attic, it really has 3 main floors, a basement, an attic, and a Cape-Cod like semi attic with 2 bedrooms. It’s in the middle of town so walking is possible (now it’s a small town so not to a bunch of places but still.) I’d prefer it to a traditional-looking mansion in the middle of a small town since it would look too much like a funeral home.
Ooh ooh ooh, the Hemingway house on Key West. Totally. It has a whole acre of well-planted land to itself, a saltwater pool, awesome outbuildings, and the house itself is just the kind of dignified symmetrical floor plan I like… and done in just the whites and pale blues and dark brown woods that I like. Plus, there are lots of cats.
And it’s on Key West. No brainer.
Easy. The Ponderosa.
Or the Lutz’s house from The Amityville Horror.
I’m easy.
It needs to be place that we can build today. I’m assuming I don’t have to worry about upkeep and taxes.
I would build a family compound like the Don had in the *Godfather *and installed it with Solar, Wind and Geothermal to ensure I would be producing far more energy than I need and can sell it back. It would invite my family and some friends to move into the compound. I would probably stay in my current town.
I would maximize energy efficiency, ensure it was well above sea level and have two deep wells.
I don’t remember Snug Harbor well enough to desire it and while I would love to visit Middle-Earth, just replicating Bag-End does not do much for me. No basement shop, no garage and very little land around it. Nope, not for me.
:eek:
Hey if I get all the gadgets in Snug Harbor and everything I would take it of course. But I just get the house and grounds without the gadgets I can do better.
As to Bag-End the ceilings are low, it really is not that large. It would be very well insulated at least. But I need a place for my woodshop, cars and other stuff. It just is not a good fit for me. Another one I have always like was Tamson House, but without the Magic it is just a giant place in icy cold Ottawa. (From the books Moonheart and Spiritwalk.)
Seriously, what the hell are YOU, an adult and presumably non-midget human, going to do with Bag End? Do you LIKE walking around bent double all day? Not to mention the fact that there is probably no toilet.
Ach! You beat me to it! What if I take the first floor and you, the second? 
Winchester “Mystery” House.
Ha! I used to work at Belcourt. Its supposed to be haunted, you know 
This is my vote, also.
And my first action upon arriving is: “Mrs. Danvers, you’re sacked. Don’t bother packing a bag; your belongings will be sent to you. If I see you on the grounds again, you’ll be the tragic victim of a hunting accident.”
Then Joan Fontaine and I would… well, I’ve said too much already.