At PAX08 Bungie is showing off one of their new maps "Assembly" (formerly known as Purple Reign). Here's a video quickly running through the map.
If the stream doesn't work just click View Video below and it should take you to a page that works.
Updates:
More Gameplay has showed up. 5 minutes this time - with killing, take a look! http://www.gametrailers.com/player/usermovies/259133.html
Here's even more, better framerate then the above video and more action than the first. - http://www.gametrailers.com/player/usermovies/259135.html
