Coolest hide-a-bed ever! Sofa beds are great with their versatile functions. But even the best sofa bed has to bow down to this: the Doc Space Saving System, which converts from a regular couch to a two-level bunk bed.
Use sink water to flush toilet - brilliant idea - I have always thought it ridiculous that we use potable water to flush our toilets! I've always wanted a containment system for hand washing water and shower water for toilets.
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) Not sure I like the idea of a 'gun cabinet' door.