It's everywhere. James and I couldn't help but show Halo3 videos @ yesterday's TechNet On The Road event yesterday in Newcastle. It was rather funny to see the faces of the audience when we started the show with a trailer that echoed the words "You are all vermin" - they were expecting a day of hard core technical infrastructure demonstrations (which we delivered) and given that the trailer starts with a blank screen while the words are spoken it was surreal.
By the end of the show yesterday I heard reports (via the Internet) that it had been estimated that a million bad guys had already been killed in Halo3 - that was within 8 hours of launch!
My favourite Halo3 image so far has to be the following one I found on Jason Langridge's blog: