Chex Quest, made by Digital Café, is a total conversion of The Ultimate DooM. It was released in boxes of Chex Cereal in 1996, becoming the first game to be included in a cereal box. When it was released, it increased sales by over 200%. It then went on to win both the Golden Reggie Award for Promotional Achievement, and the Silver EFFIE Award for Advertising Effectiveness.
16 years later it still stands to this day and is amazing to play...dam it cereal companies do this advertisment again and make sure it's as great as this.