My three favorite Strother Martin roles were:
The Captain in Cool Hand Luke. When you first see him and he's so soft spoken and easy going that you don't think he's really ruthless and although he doesn't seem to like to have to be that way, he will do whatever it takes to keep the prisoners in order.
The GM of the Charlestown Chiefs in Slap Shot. Has the thankless job of trying to keep a downtrodden hapless cellar dweller team going. Especially when he brings in the Hanson brothers. Martin-"I got a good deal on those boys". Paul Newman- "A good deal? They brought their freaking toys with them"!
And last, one of the scavenger bounty hunters in The Wild Bunch. Two of the best lines in the movie. "Look JT, It's Pike"! and later when he and his cohorts have finished loading the bodies on horses and stuffing their pockets with loot, he says to Robert Ryans character, "Well, we're all loaded up".