Whataburger is freakin' awesome. I get the triple with cheese every time. Unfortunately, the closest one to me is about 2hrs away (Texarkana, AR) so I don't get them very often. There's Feltner's Whattaburger (note the extra T) about an hour and a quarter away (Russelville, AR) which might even beat the Whataburger chain. Again, the triple with cheese is the way to go. On top of that, if you order a "large" order of frys, there's probably enough for about 3 people. If I'm near either one, I'm stoppin' for a triple.
Edit: Forgot to mention I tried the KFC Double Down the other night. It's tasty as heck, but it needs to be on a bun. Needs to be bigger too.