I'm not too much into gadgets, but this is my favourite one. It's a spring hammer to make leading holes. If you're doing a lot of metal working, this gizmo is near indispensable.
@neauoire Neat!
On a related note, i do recall finding a very cool fastening tool, called a wire clamp: https://youtu.be/mRc7ZDRcgrQ
I don't see many people talking about it in the DIY space, but I do find it elegant