Bowlers picking the ball? As long as I can remember.
Broad and Anderson have both chatted about the criteria they used and how it felt in their hands. How some balls feel smaller and harder etc
Law 4.2.1 All balls to be used in the match, having been determined by the umpires, shall be in the possession of the umpires before the toss and shall remain under their control throughout the match.
I guess it doesn't apply down under, as the balls weren't under the umpires control when the Aussies were fiddling with them!