I've been designing my dream house since I was 12. I'm considerably older now, but I've put a lot more thought into it since then. My current incarnation of the house includes the following: meat locker with whole sides of beef and pigs, indoor/outdoor pond, entryway trapdoor and slide, Velcro wall, adjacent indoor basketball court, obstacle course and shooting range, home theater, flood room, bomb shelter, armory, four-car garage, veranda, wooden deck in the rear, and gyroscope room. Most of those should be self-explanatory, but I'll focus on a few.
Indoor/outdoor pond: I like to swim, but I don't really need a pool. However I'm used to ponds, and I like koi. The indoor/outdoor pond resides halfway outside and halfway inside the living room. It is a relatively shallow stone pond than runs underneath one of the windows overlooking the backyard.
Velcro wall: As seen on Letterman, the Velcro wall is a great way to punish children, albeit in a fun way. Make them wear a Velcro suit and hang them up on the wall--facing the wall if they're particularly naughty.
Entryway trapdoor and slide: The front entryway of the house would be enclosed in a small dome. When someone rings the doorbell, you can trigger the trapdoor to open beneath them and they will slide into the basement playroom. It also makes for a quick way to get into the house.
Flood room: This room is another playroom of sorts that can be flooded up to several feet in depth. Great for acting out scenarios in which you're trapped on a sinking boat, or a scenario where you're trapped in the trash compactor with a Dianoga.
But secretly, I also have another dream house that is much, much simpler: a hamster house. I envy hamsters because their cages seem like so much fun. I like the idea of climbing through clear tubes. It's neat that they have a water dispenser that they can drink from at any time. And I always wanted a wheel to run in for hours on end. So my extra special dream house would be a multilevel giant hamster cage, but instead of wires, it would be enclosed in translucent plexiglass with blue wires running through it to create the illusion of a cage. Of course there would be clear red and yellow tubes running throughout. For privacy there would be a large, faux cardboard tube to sleep in. And I would have the world's largest hamster wheel to run in all day.