Sorry O2K, In and Out, hands down. They have fresh lemonade also.

Personally don't like Fatburger fries, and In and Out has WONDERFUL fries. Reading above that you can have the burger grilled may improve it.

We have a Fatburger 1 block from the office and our every-single-day take-out lunch group has only gotten food from there once. No requests for a repeat. It's not even on the long version of our rotation list (And KFC is, if that gives you a clue!) Advantage of Fatburger is no line ^ . (Also no drive-through , at least at our local one.)

But I must admit we have George Burger a local 2-store place that is almost as good as In and Out, so we choose that over Fatburger.

Unfortunately, the city turned down an In and Out location years ago because In and Out wanted a sign visible from the freeway. Duh. (Apparently only auto dealers are allowed to do that )

So OP, skip the midnight buffet and head for In and Out. Then Fatburger. Then In and Out. It may be the best food in Vegas. Think of the money you'll save for gambling or buying your wife tokens of appreciation.