This deserves a top-level comment. John Britton's NY Tech Meetup demo of Twilio[0] in 2010 is legendary. The CEO had been doing it in small groups for a little while, but the whole dynamic of it changed in such a large venue. Epitome of "show, don't tell." Hard to overstate what an impact it had on the company at the time (I think we were about 25 employees).
[0]: https://avc.com/2010/08/how-to-pitch-a-product/