Jeremy Piven

Biography: Born to the founders of a prestigious, Illinois-based acting school, this offbeat comic actor has made a scene-stealing career out of playing twits (the dean in Old School), nuts (the title character in the short-lived dramedy Cupid) and funny best friends (in Serendipity, starring his real-life buddy and frequent collaborator John Cusack). But though he's been a familiar face on the small and big screens since the late '80s, he didn't become a star until he took on the flashy role of a morally bankrupt agent in Entourage, a part that earned him multiple Emmy Awards.