I went to a job talk today and realized that chalkboard diagrams are sexy. This has happened before: a lecturer is using PowerPoint, but someone asks a question and the lecturer must draw a diagram to answer it appropriately. He or she picks up the chalk, turns around, and draws from memory a diagram explaining how it is. That act is sexy.
And by sexy, I mean NerdSexy. I mean that because it's unprepared and off the cuff and completely a product of someone's brain, it's a direct window into the innerworkings of this person. And for some reason that's sexy.
Example: I'm in class a few years ago, and the lecturer, let's call him Jon Baker, is talking about ribozymes or something like that. Someone asks a question, and in order to answer it, he picks up the chalk and draws from memory a few nucleotides linked together. Now, I'm a genetecist. I love DNA. So this, to me, is hot. And now I'm a huge fan of Jon Baker.