Scott's Burgers in Bixby. They were featured in Southern Living magazine a while back. Small place, friendly folks, tasty burgers.
I've been there; I didn't think the burgers were all that great. Good, but not great. I'd rather get a burger from Claude's on Peoria (across from Weber Root Beer, another good burger place). But for a GREAT burger, Kilkenny's on 15th St in Tulsa serves an awesome butter slip burger.