If you believe the surveys, public speaking.
Researchers have found the fear of speaking in public ranks right up there with a visit to the Pearly Gates. Even CEO's shudder at the thought. In many cases our fear is tied to imposter syndrome. We are afraid people will discover our flaws or worse, realize that we don't really know what we are doing.
There is no easy way to extinguish that fear and we shouldn't try to. A little fear can help motivate us and push us to be better. What you do want to avoid is letting that fear take over and prevent you from participating. This article from the Atlantic gives a couple of great tips that I have used over the years, including focusing on the present.
If you are speaking at an event, paying attention to the audience, the other speakers and the reason you have all gathered can shift the focus away from your fear. I like to think about events as a conversation that is happening in real time. In a good conversation you don't focus on yourself; you listen, engage and respond to your partner. If you can remember to do that when you approach the microphone, it will help ease those jitters and ensure you don't just survive the event, you enjoy it.