For me what best demonstrates how Martok was written so genuinely Klingon is in the finale; while Sisko and Admiral Ross refuse to toast their taking of Cardassia because of the mass slaughter that has taken place, Martok relishes in his victory, chuckles at the humans "ethics" and guzzles his bloodwine. I love it when aliens don't conform to humanity's own sense of morality.
That is exactly the scene that I was thinking of. Just when you thought Martok might be getting a bit too 'human' amidst all the Dominion-squashing, he revels in the realities of war as only a Klingon could. His arguments with the Romulans at briefings were always fantastic too - so easy to wind up and antagonise!
I also loved his relationship with Sisko. Those guys were brilliant in their scenes together, such honest dialogue. Two working class, middle-aged men who really understood each other's positions and responsibilities, as soldiers, as leaders, as fathers, as husbands. I loved them both.
Incidentally, has anyone read JG Hertzler's Martok
novels. The adventure is a bit crazy in places and Martok is presented as a bit of a mythic hero
sort of Klingon but they are a damn good read if you ever liked Martok and Klingons.