Dan Quayle has provided lots of material for David Letterman but the "Late Night" host sounds genuinely perturbed about Quayle. Letterman, who is 41 years old and from Indiana just like the Republican vice presidential nominee, says he recently watched a videotape of Quayle speaking and was unimpressed. "I thought I saw gaping shafts of light going through his skull," Letterman says in Rolling Stone's special comedy issue. "Then I saw him in Wyoming and some reporter asked him, `What message do you have for farmers?' And he thought and began to say something, then he decided not to say anything and just smiled."