The object of everybody’s search in movies – the power cube, the energy crystal, Marcellus Wallace’s briefcase?
Turns out theres a name for these objects – a MacGuffin:

In fiction, a MacGuffin (sometimes McGuffin or maguffin) is a plot device in the form of some goal, desired object, or other motivator that the protagonist (and sometimes the antagonist) is willing to do and sacrifice almost anything to pursue, often with little or no narrative explanation as to why it is considered so desirable. A MacGuffin, therefore, functions merely as “a plot element that catches the viewers’ attention or drives the plot of a work of fiction”.[1] In fact, the specific nature of the MacGuffin may be ambiguous, undefined, generic, left open to interpretation or otherwise completely unimportant to the plot. Common examples are money, victory, glory, survival, a source of power, a potential threat, a mysterious but highly desired item or object, or simply something that is entirely unexplained.

Thanks Bryan.