Well for me it goes to a Juve icon who's under 30:
Buffon
Zambrotta
Ibrahimovic
Camoranesi
Trezeguet
Okay we can remove Zlatan immidietly.

Trezeguet we aint sure of how long he'll stay and Camoranesi doesn't seem like a leader to me. So my choice goes between:
Buffon
Zambrotta
So only one of those I see as a leader, but he's also a goalkeeper. The other one is a true hard-working fighter, who can inspire. I got to go with number one. I just can picture me calling Zambrotta capitano.
Buffon fo' president!