Really Right Stuff L-Plate (£85, $140)
What’s it for? It mounts on the bottom and side of the camera (or battery grip) and enables the camera to be placed very securely in either landscape or portrait mode on the tripod head or camera stand.
Plus points It works with the Really Right Stuff quick release clamps that I have mounted on my two tripods, camera stand and video tripod, so I can easily switch between setups.
Minus marks None that I
can think of.