Arnaud Lapierre's doorknob design just made me laugh for its sheer obvious ingenuity. No, this isn't going to stop an experienced burglar, but it will surely keep out the kids when Mom and Dad need some "quality time" together. The knob works using an internal pulley system in which the one knob is pulled inward and locked into place, leaving the exterior knob flush flat. More photos here.
[via Yanko Design]