I'm at work, Candy, so don't have the recipe, but I use a classic beer batter and double-dip the rings. Slice and separate onion rings, dredge in flour, dip in beer batter, re-dip in flour, dip a second time in batter. The rings are always feather light and soooooo yummy. I hate the thick, dense things they serve at fast-food restaurants. If you'd like the recipe, I can dig it out when I get home.
I soak the onions (generally mayan sweets) in a mixture of 1:1 buttermilk and hard apple cider with a dash of Dave's insanity before throwing them in a paper bag with seasioned flour (flour, cayenne, lots of fresh ground pepper, salt) and then tossing them in the oil. I slice them up pretty thin, so they aren't true jumbo rings. I get lots of requests to make them, so I assume they are tasty.
I also deep fry shallots in similar flour mixture and olive oil to top roasted asparagus at dinner parties. I often get requests for just a basket of fried shallots, but talk about a ton of prep work, making all those little mini rings!
The batter I used for fish n' chips the other night was amazing for onion rings. Very crispy, airy, yum. I ate way more onion rings than fish.
Previous post, with recipe: http://www.chowhound.com/topics/show/...