Contrary to popular belief, the MacGuffin is not a flatulent Scottish seabird; it is the mysterious object used solely as a plot device in various story-telling media. The name 'MacGuffin' is slightly mysterious. Many attribute its coinage to Alfred Hitchcock, who claimed to have first overheard it on a train as part of an exchange between two Scots. This story is considered highly dubious.
So, What Actually is it?
This is the thing. To qualify as a MacGuffin, the actual form of the object is irrelevant. What is important about the object is that in itself, or in its potential, it is a source of motivation for the characters - be it the priceless jewels hidden beneath the black enamel of the statue in The Maltese Falcon, the infinite power of the Ark of the Covenant in Raiders of the Lost Ark, the mysterious contents of Marsellus Wallace's briefcase in Pulp Fiction, or the radioactive Chevrolet in Repo Man. What's important is how these objects cause the characters to act, and in fact that these objects could be swapped freely between films without changing the plot.
It is the mechanical element that usually crops up in any story. In crook stories it is almost always the necklace and in spy stories it is most always the papers.
- Alfred Hitchcock
I Want One!
Don't we all. Although many films from a diverse list of genres contain MacGuffins, those who seek an easy MacGuffin would do worse than familiarise themselves with these famous genres of film and literature:
MacGuffins can be practically anything, and may not even be defined as an object. It is this flexibility that has allowed the MacGuffin some strange incarnations over the years. For example, R2D2 in the Star Wars films is described as a MacGuffin by George Lucas. The meaning of the word 'Rosebud' is the MacGuffin in the film Citizen Kane.
Some films deliberately distort, swap or misrepresent a MacGuffin. For instance, the MacGuffin in The Jewel of the Nile is the titular and highly valuable 'Jewel' that, after much quality motivational action, turns out to be an intensely bearded person. Woe is Michael Douglas. Another example of this would be 'the Army of the Twelve Monkeys' from the film Twelve Monkeys, which at length turns out to be mere nutty animal rights activists and not the cause of the apocalypse.
Some films share a MacGuffin. The best example of this is probably the Holy Grail sought by everyone from King Arthur to Indiana Jones' dad, followed closely by 'government secrets'.