10. Anything By Gilderoy Lockhart
Look, I know it's sort of a cheat nothing Gilderoy Lockhart ever wrote had a lick of sense in it, so you might argue that basing anything on what is effectively a lie could seem nonsensical. And fair enough, I get that opinion, even if his whole canon did feature awesome alliteration (see what I did there?) But let me ask you this why not use the blatant lies to make it better? You could totally play all the dishonesty for laughs. As was made abundantly clear throughout the Chamber Of Secrets, Lockhart is nothing if not a shameless self-publicist who always wants to cast himself in the best possible light, even if he has to resort to blatant lies. So why not have a story that's freeform, and constantly mixing itself up to portray Lockhart as an all conquering hero? Picture it with Kenneth Branagh reprising his role in narration, you could have the hero gradually getting younger, stronger and more handsome as the story goes on. He could tell you he was fighting three Banshees, then stop the story, tell you they were bigger and more numerous, and have the scene change on the fly. To my money, it would be a great story that could work not just as a Harry Potter companion piece, but as a rip-roaring comedy and a great satire of one-man-army films. Honestly, what's not to like?