Not a gadget exactly, but I love my chef knife! It’s a Kan core chef knife. I have had it for several years now and enjoy using it every time. It is very sharp and is easy to keep sharp. It was not cheap, but not terribly expensive when compared to other professional quality knives. I use it almost every day and it has never disappointed me.
For actual devices in the kitchen, I would say my Kitchenaid stand mixer is my favorite.