I'm having a clear out of stuff I either don't, or have never, used. An example of this is the Manfrotto suction mount which has been sitting in my drawer because having bought it I've never managed to convince myself to put a heavy and expensive camera and lens on it, so it's going on Ebay, where it will no doubt give years of service for someone with a GoPro. When I started doing wildlife photography a lot of the specialist kit, such as radio releases, had to be home made and I've got another drawer full of these specially made bits and pieces.
What have you got which you thought was a good idea at the time?