Billy Mays was the pitchman on TV commercials who yelled at the camera. An article about him discussed his style:
The hardest part of making a sale is stopping people, whether they’re wandering by a booth or flipping channels. For Billy his volume, energy, hand gestures, and faux authority (“Hi, Billy Mays here for …”) are all tactics to get attention and build excitement.
Sometimes we make the mistake of thinking that in a presentation we don’t have to worry about stopping people and getting attention because they’re in the room across the table from us. But don’t confuse having their physical presence with having their actual attention and interest. You always need a strong open to draw focus and build excitement, even if it means setting your hair on fire.