Robert Kennedy. His extemporaneous speeches are some of the best I’ve heard.
Ben Shapiro is a very influential and entertaining speaker, but his style reflects being more argumentative than powerful speaking wise, but that makes since as a political figure.
If you’re talking about speaking, I’d think some philosophers ought to be in this list (and I saw some).
The Bible is a potential, having been one of the most read pieces of all time. It’s influence spreads much farther than any one speech/hearing.
Not that this is an individual speaker, but I enjoy hearing the passion behind speeches by revolutionaries/rebels.