Four trailers were shown of Super Smash Bros. Brawl. With the exception of the trailer shown at Nintendo World 2006, these trailers are included in the game itself. The first trailer that revealed the first ten playable characters (Mario, Link, Kirby, Pikachu, Meta Knight, Pit, Samus, Zero Suit Samus, Wario, Snake) was shown at E3 2006 on May 11, 2006. The second trailer revealing Fox returning as a character was shown at the Nintendo World 2006 convention in December. The third trailer revealing Sonic as a playable character was shown at the Nintendo Press Conference on October 10, 2007. The fourth is just the game's introduction.
Nintendo World Video
Sonic Reveal Trailer
Super Smash Bros. Brawl Introduction