Y'all should hire him, he's the new Stan Freberg.
http://www.youtube.com/watch?v=8FC_eMDnCRg
Thumbtack; saw this because they just got funded through Venture hack's Angel list.
They're all in Berlin. Nuts.
http://www.youtube.com/watch?v=MVVui4oXL4Q&hd=1
Aside from high production values, the reason this is a great clip is that they start with "Why?". If you're not familiar with Simon Sinek's awesome TED talk, I highly recommend it:
http://www.ted.com/talks/simon_sinek_how_great_leaders_inspi...
That being said, it's just a simple screencast, so I wouldn't say it's inherently creative or out of the ordinary. But it does go to show that you can make a decent quality demo video on the cheap in under a few hours if you take it seriously.
EDIT: Oh, and just in case you'd like to see it: http://s3.amazonaws.com/leadnuke-com-cdn-streaming/introduct...
http://www.youtube.com/watch?v=diTpeYoqAhc
In a similar vein, the famous "Twitter in Plain English":
http://jonbischke.com/2009/11/13/a-dozen-of-the-best-start-u...
Though not a product demo, but the way of explaining it in simple words and illustration makes it stick to my mind.
Take a look: http://dabbledb.com/demo/