Halo 3 video with X button footage -- Is Quisnam Protero Damno!

Accompanying the revelation that the Halo 3 multiplayer beta is coming May 16th (OMG!), was the above Vidoc (video documentary we imagine) dubbed "Is Quisnam Protero Damno!" (Any Latin majors reading?) Included in its roughly 7-1/2 minute runtime is footage of two new defensive functions and something entirely different:

• The bubble shield, first spotted in the Starry Night commercial

• The just-revealed trip mine, shown taking out an incoming Warthog (and the player)

• And a replay function you can share with friends, to slow down or even pause that perfect headshot (perfect for bragging rights)

So exactly which features are activated by the mysterious X button? In his update at Bungie.net, Frankie said, "There will also be new guns, vehicles and gameplay features to try – including the mysterious 'X-Button' functionality. But you don't have to wait to find out what that is, since you can now view part of its functionality in our latest Vidoc ..." Part of its functionality, eh? Need more proof? An alleged IRC chat sent in by reader Kritz had Frankie confirming, "x button deploys equipment for great justice. :) bubble shield and tripmine announced so far." So far, eh? What else is up that comically billowing sleeve of yours, Bungie?