I'd go with:
Jacques Kallis
Chris Gayle
Mahela Jayawardene
Kevin Pieterson
David Hussey
Eoin Morgan
Brendan McCullum
Shahid Afridi
Dale Steyn
Umar Gul
Saeed Ajmal
Gayle and Kallis would be an amazing opening pair, their styles complement each other perfectly, plus thats a left-right combination. The Middle order looks pretty strong too. KP and Jayawardene are in magnificent form and can stabalize the innings and play their shots at the same time. David Hussey and Morgan are great @ 5 & 6. Again they can play the huge shots and consolidate as well. McCullum is there as I need a keeper and he could be an important finisher down the order. Afridi takes the All-rounders spot with ease and even the bowlers can hit out a few.
The bowling looks great. Steyn to start things off, and the new ball goes to either Gul or Kallis. Afridi could come as a first change and they valuable part time options in KP, Hussey and Gayle. Plus in the depth their bowlers like Ajmal, who is an underrated T20 bowler, and Gul. Heck Even Steyn can bowl there.
Looks like a very strong team that
Missed Out:
Watson - With Gayle and Kallis opening there is no spot for him, as Kallis can bowl Watson's medium pacers instead, and Gayle has the aggresion.
White - Would like to him there as well, but Hussey gets the preferance.
Vettori - Afridi takes the all-rounder spot, so there is no place for him.
Malinga - Was a case between him and Gul, but I'd prefer Gul over him.