For Augustus, the scene in the bar is my most memorable. He makes the speech about not taking any lip from uppity bartenders after he smashes the guys face in the bar for being disrespectful. But his character fell short in the long run simply because his character was martyred in a non iconic way. I would argue that Val Kilmer's Doc Holiday was more iconic. Though I did enjoy the character very much.
For Woodrow, everyone looked up to his character and he was able to back up the call for that respect numerous times through the movie/series, but the one that stuck home for me was when he took that soldier/officer/scout(??) that was horse whipping his son and nearly killed the man. McCall's actions and cold expression in that scene showed us all, the lengths he will take to demand respect for himself and those in his protection. His determination to return Gus to his final resting place drove home his loyalty and devotion.