A surprising favorite o-ring for me is Popeye's, but it can be hit or miss:
First off, I don't see them at all units, some have "onion petals" which is pieces of a disassembled blossom, too salty, with a cornmeal breading.
Second, the rings are occasionally fried too long or at too cool a heat, yielding a hard leathery exterior.
But when they're good, they're great: wide cut (about 3/4") sweet onion rings ranging up to 4 1/2" across, with a tempura-like light batter, and a fair amount of red pepper for spice.
What is patriotism, but the love of good things we ate in our childhood?
-- Lin Yutang