We moved into a pretty cozy place and there isn't really a place to hang out, besides the living room couch. So I don't have a favorite room in my house right now! Usually though, my favorite room is wherever there is a comfortable chair where I can read and nap... or the room with the computer in it.
For my kids, their favorite room is our "classroom": it has lots of arts and crafts activities in there, tons of books and most important: air-conditioning!