Spice
Spice is the sole most expensive substance in the known universe, granting longlivety, immunity to certain poisons and diseases, and allowing people with predespositions to awaken their prescience. [1]
Spice in game
Spice will be a very important part of Dune: Awakening as Arrakis is the only planet where it can be found. As such, it will be a source of wealth, as well as allowing you to alter certain skills, the current effects are unknown. Spice is highly addictive, and requires maintaining a certain level, or face the consequences.