There are so many good freekick takers: Henry, Rivaldo, Juninho, Del Piero, Pirlo, Beckham, Van Hooijdonk, Ronaldinho, Mihajlović, Totti, Deco, Roberto Carlos, Zidane,...
But if I have to choose one, I´d say
Juninho.
Mehmet Scholl used to rule freekicks, but now Juninho is new emperor.