Probably Sebastian Vettel
The defending Formula One World Champion heading into the 2012 season is Sebastien Vettel of the Red Bull Racingchassis.
Sebastian Vettel
As of July 2014, Sebastian Vettel is the current Formula One World Champion driver, having won the championship 4 years in a row: in 2010, 2011, 2012 and 2013.
Big show is the world heavyweight champion
CM Punk is the WWE Champion
There was no World Cup in 2012.
Big Show is the current WWE World Heavyweight Champion as of December 2012. He defeated former world heavyweight champion, Sheamus, on the 28th October at Hell in a Cell
The 2012 and 2013 World Professional Snooker champion is Ronnie O'Sullivan.
Sebastian Vettel
Yes
Jenson Button entered the 2010 formula one season as the Reigning and Defending drivers world champion because he had won the 2009 drivers title. Sebastian Vettel won the drivers world title in the 2010 season from Fernando Alonso by just 4 points. Vettel has been the defending world champion ever since because he won the titles 3 consecutive times in 2010, 2011 and 2012.
Formula One also known as Formula1 or F1 and referred to officially as the FIA Formula One World Champion is the highest class of single-seater auto racing sanctioned by the federation International of Automobile (FIA). The numbers of spectators who watched the F1 World Championship in 2012 was about 527 million.