It was January 9, 2007. Steve Jobs was on stage, about to reveal the iPhone, arguably the single most influential tech product of the last 30 years. After a few minutes of buildup, Jobs got to point, saying, “Today, Apple is going to reinvent the phone, and here it is..."
Jobs gestured to the screen, as a photo of the first-generation iPod with a rotary phone dial appeared. The audience burst into laughter.
At the moment of truth, with his audience breathlessly waiting to see the phone that would change everything, Jobs went for the joke. It worked. 
In almost any situation, laughter elevates the mood. If you’re able to give your audience that gift, I encourage you to give generously!
Here’s the video of the iPhone reveal. Start at 2:16 if you just want to get to his laugh line. Better yet, invest 14 minutes to watch the whole thing, it's a classic.