I don't care that he's not on the list, my favorite orc is Nazgrim. He's the only orc I've gotten to know on a personal level. To the players, Nazgrim is not just a friend, but a companion, and to fight with him through 3 expansions before facing him in an honorable duel (even though 10v1 or 25v1 is not exactly honorable...) was the most meaningful fight in SoO.