This may be something too small to call a "gadget", but I love these magnetic measuring spoons. They nest like a normal set but stick together in the drawer so you never spend a minute looking for a missing one that moved to the wrong spot. There are about a million varieties on Amazon and elsewhere.
A couple of my choices were already mentioned (microplane and mandolin) so here's another worthy addition. If you like pepper as much as I do, your regular pepper mills drive you insane with their measly output. Insert the UNICORN!