Adding a wall bed to your guest room will let you reclaim the space for a multitude of other uses when you're not playing host to family and friends. Mount a giant flat screen opposite the bed, and add dimmable lighting, seating and surround sound speakers for a home theater. Build in an adjoining desk and filing cabinet to create an instant home office. Custom wall beds will also save you floor space so you can keep a treadmill, yoga ball and free weights for a home gym. Or try adding a dressing room so you'll never have to worry about stuffing your whole wardrobe into a bedroom closet again.