My favorite would have to be the Redguards, due to their fiery and individualist attitude. I really like the culture in Hammerfell we've seen through Daggerfall and Redguard, and they still have some of the best combat taunts in the game. My second choice, if there were one, would be the Nords for their wonderfully shamanistic culture and because they're probably the most organized and resolute humans on Tamriel after the fall of the Empire. Their culture gives the air of ancient tales and primal fears, stories of greatness and tragedy, legendary creatures and magical powers. The Bretons and Imperials are just too tame, in my opinion.