In-n-Out.. yummy. Five Guys is good, but pricey.

Skyline is good.

A new one to add... Rubio's on the west coast. Fish tacos... yum... and their fresh salsa is some of the best I've had, and doesn't make me think it's really "fast food".

Another Mexican place, that's more of a "casual dining" than fast food is Chevy's, even though my local Mexican place here in WV does better than Chevy's many times, but Chevy's version of salsa is just so tasty.