Will you share your favorite YouTube videos?

I’ve started getting more into YouTube recently. Jeruba’s recent challenging question made me find some new ones I love just yesterday. There’s so much out there – will you share your favorites?

This makes me crack up, but I’m not totally sure it’s real.
This is a great song I can only access on YouTube. And here is the best live performance I’ve seen so far on there.
And I think this might be the most hilarious commercial of all time, but it is most definitely NSFW, so please be warned.

Edit – I enjoy some of the really popular ones, too, but I think if we all found some hidden gems through this thread it would be really nice.