Well, I couldn't bring myself to rehash 13 pages of posts but of the first 30 I did read, nobody mentioned Off-Site-Kitchen. It's on Irving Blvd in Dallas (a little northwest of Oaklawn -- think the Anatole Hotel or Parkland Hospital.)
Ab-so-fucking-lutely the best burgers & fries (and yes, I've had Maple&Motor, and almost everything else.) And the 48hr cracked pepper brisket is to die for (but have them hold the cheese - IMHO it overpowers all the other wonderful flavors happening in that sandwich. It's truely a hole-in-the-wall, most seating is outdoors and it looks like a total dive - except for the line out the door.
(And if you didn't know, it's moving to that new Trinity Grove incubator space soon - which I fear means the end of $4 burger deliciousness!) Run don't walk!