For the basement stairs: cabinets, stairs with flip up steps and very narrow stairs. Each step goes up one at a time for each foot. It is sort of spaced so you are putting one foot per step with a steeper step. Very space-saving.
secret room IN the stairs! I need a secret room somewhere in my house. So have the secret room under the stairs, but to actually make it secret, don't put the door under the stairs, put it in the stairs.
I love things that hide things. I especially want that bathtub and the vent/safe. The TV hiding all the other electronics is a great idea, but I'd imagine there'd have to be some kind of sensor in order to work the other stuff.