I'm outlining a story. It's gotta a McGuffin in it.
So I am merrily working out how to disguise the fact that it exists only in order that the characters may care about it and so do stuff. Like, commit plot. Thus far I only know that it's got to have some magical properties, because one character would want it for no other reason. (She's kinda like that.) And that it has a long history. (What happened in that history? Dunno. At least yet. But I know it's long. 'cause that's why some other characters care about it.)
MacGuffins get a bad rap. You do have to motivate your characters, and people do care about objects enough to do lots of interesting things. The Maltese Falcon actually used the MacGuffin for its title -- it's not as if the story would change much if you plopped some other precious thing in there because the femme fatale has to actually want something. You'd have to cook up another lengthy history to hide the fact, no doubt. In fantasies you can add magical powers as an added distraction.
Like plot coupons, which are bad because they are creations of the author's arbitrary will. Hate to break it to you, but everything in a story is there because of the author's arbitrary will. Anything could have been different. Perhaps it is meant to mean those cases where you can tell it was the author's arbitrary whim, but -- humm, I shall paraphrase Booth from The Rhetoric of Fiction: all that says is when you do it badly, the results are bad. Which is not the most useful piece of writing advice.
So I shall return to detailing my MacGuffin to disguise my hand and appreciate the other advantage: because I have such a free hand, I can make it symbolic and other useful things for the plot.
I think I'm going to make it have been a gift in honor of something.