Here is the cross post of an answer I gave on Quora:

No, don’t use Steve Job's famous "one more thing" at the very end of your presentation

• When you are starting out with pitching your venture and you do not have the track record of Steve Jobs (yet), it is not smart to leave your biggest point to the last minute
• It is very hard to assess whether using humor in a presentations will work given the meeting dynamics. Hard-wiring a “joke” in the sequence of your slides removes the flexibility of playing it safe and pulling the joke when the mood in the room just does not feel right
• Around most of Apple’s releases there was some sort of anticipation of something big and new that was coming. Often, details of product were leaked in the press. The product had actually already been pitched before the presentation started. The audience was just hungry for the details. In a pitch or interview this is probably never the case.

Cover image by Ben Miller on Flickr