Hidden doors -- This company makes cabinets, bookshelves and anything you can think of that fits your existing doorjambs thus hiding the door (and also making use of the space). If you click through checkout the "gun cabinet" door. Lots of great ideas.
You can make anything by recycling the pallets, from a sofa to a bed and a side table to a book table. There are no bounds or limitations, make anything you want and place things around it to enhance the looks even more. See the picture and make something that can be used for different purposes like as a sofa and as a bed both.
21 Ways Of Turning Pallets Into Unique Pieces Of Furniture