Equivalent of "former" and "latter" for more than 2 items
Former and latter are valid only when there are two choices.
If I have a list of more than two items, is there an elegant way to say the first one or the last one?
You can say first and last (without one).
Of winter, spring, and summer, I find the last most enjoyable.
I don't think there's anything inelegant about first or last. You can always use ultimate, penultimate, and antepenultimate if you want to be certain no one understands you.