The most recognizable living person today is…

• an actor
• a movie or theater staff
• an announcer or talk show host
• a writer
• a musician
• an other kind of artist
• a website or game designer
• a businessman
• a sportsman
• a sports leader or coach
• a scientist
• not a scientist though claims to be
• a religious leader
• a politician or military leader
• an activist
• a royalty

The above works alone too, but you might also do a second poll later similar to the following.

The most recognizable contemporary sportsman is

• Lance Armstrong
• David Beckham
• Roger Federer
• Michael Jordan
• Garry Kasparov
• Michael Phelps
• Michael Schumacher
• Mike Tyson
• Tiger Woods

(I gave sports as the example because that's the one for which it's the easiest to make a reasonably long but varied list of very famous figures.)

Update: added "businessman"; changed Cristiano Ronaldo to David Beckham, for the latter is more famous.

Update: in fact, the second poll (the one about sportsmen) might work alone too.

Update: you may want to add Björn Borg.