If you come up by Lawton stop by Ft. Sill Apache Casino. It's pretty much a giant tent, but when you walk inside you'll be surprised. 2 stories, escalator, elevator (big stuff for this little city!)
Like most casino's in the area, we are mostly a slot joint. We got a full bar and a very good little cafe downstairs that will grill you up a burger or steak. 1 full pit of blackjack, baccarat table, ultimate texas holdem, 3 card poker, and even craps (oklahoma craps is played with cards.)
I'm the surveillance manager so i'll be watching! :P
As someone else said, WinStar is by far the most visually appealing and very large also, the Firelake Grand Casino is Shawnee is fairly new so its really nice too. RiverWind in Norman is also a wonderful place, but really crowded - as most casinos here are, but they have alot of shows going on and Norman is a much larger city then shawnee or whatever town winstar is in [middle of nowhere] - another good option is Lucky Star Casino, although I have never been there myself I know its a very popular place.