David Letterman does it. Arnold Schwarzenegger does it. Even Sharon Stone does it. In fact, the new favorite pastime of the stars these days is sucking on a stogie. "There are celebrities smoking cigars where years ago they didn't want to be associated with tobacco," says Marvin Shanken, publisher and editor of Cigar Aficionado. "The median cigar-smoker age is coming down like a rock. It's now a step toward becoming a man." At Schwarzenegger's Los Angeles eatery, Schatzi on Main, there's a two-week waiting list for the star-studded "Cigar Night" ($50 for a four-course meal, two cigars, and port). But Shanken rejects one of the most high-profile puffers: "Madonna is not somebody I would hold up as a cigar smoker," he says of the singer, who lit up during her notorious appearance on the Late Show in March. "She gives cigars a bad name. She's no class act."