Retractable Corded Mouse
You know those phone cords with a spool on 'em so they're constantly under tension and retract completely when you let go? One of those for a mouse.
Why It's Awful
Every time you took your hand off the mouse it would fly clattering across your desk and end up hanging from a USB port behind your tower. Expect it to knock your coffee over at least twice before you go back to wireless.
People are really into cord management so... there's that. But really not even the most orderly of people wants their mouse dangling from a USB port every time they let go of it. Every. Single. Time. Adding a locking toggle to it would add usability but that's not the point here.