Trailer

An Announcement Trailer is often used by gaming companies to introduce new games into the public view. These trailers are often pre-rendered (Meaning they do not show actual gameplay footage, but rather a cinematic) and filled with action in order to excite the game fans.

Bungie has released Announcement Trailers for Halo: Combat Evolved, Halo 2, and Halo 3. Ensemble Studios released an announcement trailer for Halo Wars

Note that these trailers are sometimes created in the midst of game development, so, quite often, footage seen in the trailer is modified in the final game, or changed altogether. Because of this, it is sometimes difficult to consider the information in the announcement trailer as canon.

Announcement Trailers

 * Halo Announcement Trailer
 * Halo 2 Announcement Trailer
 * Halo 3 Announcement Trailer
 * Halo Wars Announcement Trailer