By now Margaret has me completely converted to shallots as the all-purpose members of the onion family (as our friend T had taught her).

I use other kinds of oniony things for special purposes:

red onions	raw in salads	because they're mild
scallions	both cooked and raw in Asian cuisines	because they taste right
scallions	in scallion biscuits, pancakes, frittatas, and omelets	because they taste like ... scallions
white onions	in Mexican cooking	because they're low-sugar, which is what makes them taste right
yellow onions	for making large quantities of browned onions	because they're easier to peel en masse than shallots

But when there's no special reason to use some other kind of onion, my go-to is the suave, full-bodied shallot. I use them both raw and cooked, but when they're raw I want them cut very fine.