Every businessperson wants and needs to be an effective public speaker. To accomplish that, however, you need role models in every category of public speaking. Here are the best of the best:

1. Product Demos--Tony Stark

The purpose of a demonstration is to show how a customer's life or workplace will be different after purchasing a product.
The least effective product demos are "spray and prays" where the demonstrator walks the customer through every feature and function of the product. Borrrrringgggg!
The most effective product demos tell the customer's story with the customer as the hero and the product as the "magic sword" that allows the customers to achieve the goal.
Even though he was playing a fictional character, the most "blow them away" product demo in history was presented by Robert Downey Jr. in the first Iron Man movie.

2. Presentations--Steve Jobs

The ostensible purpose of a presentation is to convey information concisely, using a combination of bulleted lists (aka talking points) and detailed graphics and charts.
Every presentation, however, has a hidden purpose, which is to persuade the audience that what you're saying is meaningful and important.
The best presentations combine passion and information along with compelling arguments that reinforce the relevance of what's begin said.
Steve Jobs was the absolute grand-master of great business presentations. Even on those rare occasions when he was introducing a so-so product, his sense of conviction remained contagious.

3. Speeches--Tony Robbins

Like a pitch or presentation, a speech must to motivate and inspire the audience. However, speeches have are inherently less interactive. If there are questions, they're typically asked at the end of the speech.
There may be some visual aids in a speech, but the focus remains on the speaker. In large venues, a close-up of the speaker is displayed on a screen above the podium.
Unlike presentations and pitches, speeches tend remain more or less the same for every audience. As such, they're more rehearsed and polished.
There's no question in my mind that the best public speaker alive today is Anthony Robbins. While some people find him grating, there's no question that he grabs your attention and holds it better than anyone alive today.

4. Panel Discussions--Guy Kawasaki

The purpose of a panel is to inform and expose the audience to differing perspectives on a single issue.
Panels begin with a moderator introducing each panelist, who gives a short presentation outlining the position the panelist is taking on the subject matter.
The moderator then asks questions of the panelists in order to draw out and clarify the positions that each panelist has taken. Questions are usually taken from the audience.
The role model for panel moderatation in the business world today is Guy Kawasaki. In addition to the video, check out his advice for panel moderators.

5. Webcasts--Marsha Collier

A webcast is an informal one-way discussion, typically using an inexpensive web camera. The best webcasts are chatty and personal, which makes them challenging as a business communication tool.
The most important thing to know about webcasts is that, although they're very easy to make, they're very difficult to make interesting.
The business and sales guru Marsha Collier is one of the very few who has managed to combine intelligent content with a relaxed and friendly manner.

6. Podcasts--Kerry O'Shea Gorgone

Podcasts, like webcasts, are a fairly new communications medium for the business world. In format, they're very much like radio interviews, but unlike radio (which tends to be news-driven), podcasts can carry a story or a theme for many episodes.
Over the past six months, the podcast Serial has upended everyone's idea of what's possible using this medium. The business world hasn't quite caught on to this kind of story-telling, so meanwhile the best role model for a solid business podcast is the ever-engaging Kerry O'Shea Gorgone who does a weekly podcast for@MarketingProfs. 

7. Sales Pitches--Ron Popeil

The purpose of a pitch is to persuade the attendees to make a decision. As a general rule, they follow this pattern: 1) current problem/opportunity, 2) proposed solution/initiative, 3) desired decision/next steps.
Think of sales pitches as presentations on steroids. They only include information that's relevant to the audience and, most important, they drive to the "close"--the next steps (usually buying) that you'd like the customer to take.
Traditional sales pitches have fallen out of favor in recent years, but if there's any person alive today how can make a killer sales pitch, it's living legend Ron Popiel. During a sales pitch on live television, he once sold around 10,000 rotisserie ovens worth over $1 million... in a single hour. Amazing!

8. TED Talks--Amy Cuddy

The TED Talk is a newly-evolved hybrid of a speech and a presentation. However, while speeches can be about anything, TED talks are usually built around the speaker's journey in discovering and understanding something new or interesting.
Like speeches, talks may contain a few graphics or photographs to illustrate the subject of the talk and questions are held to the end of the talk. However, TED Talks are they're shorter than speeches, typically 20 minutes or less.
The best TED Talks combine a compelling personality and with a fascinating subject matter. A perfect illustration of this combination is Amy Cuddy's discussion of body language.