Smith, brilliant temperament. Most 22 year olds new to international cricket would be intimidated by experienced players like Donald, Rhodes, Pollock etc, let alone be thrown into the captaincy and lead them! He's mentally tough and has improved them over the last 2 years and as a 24 year old still has alot to learn, so I think he's got to come close to topping the ranks of this thread.
Then Ian Bell, has been slightly mechanical in the past but has a very solid technique and has learnt alot from the Ashes experience. De Villiers is very good, disappointing for him to be left out of one-day sqauds lately. In terms of domestic players, Ferguson of South Aus. is promising, and Allistair Cook sounds good.