@ThatGirl, it's a Maori (the native people of New Zealand) war dance. The NZ rugby team (called the All Blacks) have performed a particular haka called "Ka Mate" in front of the opposition before each game for over 100 years; this has solidified it's significance among all New Zealanders (and to the sporting world). It's associated with masculinity, aggression, pride and unity, and seeing one performed up close is scary as hell!
A second haka has been performed occasionally by the All Blacks called "kapa o pango" for the last 6 years, of which someone posted a picture of before:
[YOUTUBE="http://www.youtube.com/watch?v=cle20lQg0Qs"]All Blacks performing Kapa O Pango[/YOUTUBE]
INFP 4w5 so/sp
I've dreamt in my life dreams that have stayed with me ever after, and changed my ideas;
they've gone through and through me, like wine through water, and altered the colour of my mind.
- Emily Bronte