Another vote for shallots, although that’s in no small part due to my growing them. There are a few varieties of shallots out there, but they aren’t as easy as onions to find. I keep leftover pieces of 1/2 white, red, and yellow onions as well, and usually end up using them in some recipe within a week ( I make the serious eats puffy taco filling weekly), but will toss them if they aren’t “right” .
I love an old article from Saveur about alliums. I think this is it.