Locally:
Red Zone, the former Bob's location at Sooner Legends, the former Ramada, at SW24th and Lindsey in Norman.
Vann's, on N Porter in Norman (also in Shawnee, Moore and maybe elsewhere)

Other noteables elsewhere in the state (listed aphabetically):
Bad Brad's - outside Pawhuska
Leo's - OKC
Meer's Store - Meer's, NW of Medicine Park
Wall's - Woodward
Wild Horse - Hwy 59 S of Sallisaw (I still miss Hubert)

So long as I am within a 2-3 hour drive of any of these great places, I'll likely not find reason to visit others. One final memorable place for me was Slick's in Muskogee, but I've not been there for decades. If memory serves, Slicks is long since gone, but it was a fav in my younger days on trips with my pop.