Best. Lip Dub. Ever. by UBC (video)
What I loved was that I could not anticipate a single scene. Whenever I thought it was slowing down suddenly they would do something completely surprising. I don't want to spoil it for anyone so all I'm gonna say is: omg the pool. There. Now you have to wonder WTF that means until you get there.
Check it out and then if you've seen anything comparable, leave a link in comments!
(Source: One Cool Thing A Day)