I had one today, and it will not be built for a few days:
A lockable tape rack on my paint cart. It seems everybody believes that tape just grows in my shop. When somebody needs tape, it is take, take, take tape. Screw that noise. Enter the lockable tape rack.
It is four pieces, counting the lock. Two 3" square tabs with outer corners rounded and a hole in each to accept the 1/2" rod; one end bent at a 90 and the other will accept the standard lock. Simply weld the tabs to the vertical legs of the cart and insert the rod with the tape rolls upon it. Apply the lock and watch the fumbling begin.
Not necessary in your personal space, but needed if you are in a common shop.
Shufflin' through the parking lot of an invisible 7-11