Fish tank in the ceiling. (I would either all asleep as soon as I walked into the room . or constantly be terrified that the ceiling was going to collapse. All in all, probably won't be part of my dream house.
Adults need to have fun too! Any slide for adults in a house is a great idea, but this one contains a water slide. Excellent choice of transportation and you can even get a shower on the way out of bed going down to get breakfast!