Even though the Harry Potter series isn't the most well thought out fantasy series some of it's magic could indeed be highly useful in the real world. For example when you watch a scary movie that creeps you out too much you simply cast the "Ridiculus"-Spell and all's good:
1. Roman Polanski's "Chinatown"
It doesn't even have to be a horror movie - I always found that the scene in which a thug sticks a knife up the nose of Jack Nicholson's character and cuts it in Chinatown to be cringe inducing. But no longer: RIDICULUS!
2. Christopher Lee in "Dracula"
Many movie buffs agree that Christopher Lee played the scariest Dracula ever - and no wonder, the guy is just that intimidating! Or is he? RIDICULUS!
3. The creepy child murderer in "M"
"M, eine Stadt sucht einen Mörder" is a really old crime story that still manages to impress - the cinematography and direction are far ahead of it's time and the dramatic villain is a thing to behold. Only - with all the bad things happening the movie *could* need some comic relief, to be frank... RIDICULUS!
4. Darth Vader in "Star Wars"
One can argue that Lucas himself cast a Ridiculus on the whole Star Wars franchise himself, but if we ignore the prequels, then Vader still is a classic scary villain. Until we cast RIDICULUS!
5. John Carpenter's "The Thing"
Last but not least we have the nightmarish, monstrous, inhuman THING from John Carpenter's adaption of the short story "Who goes there?". But it will never haunt our dreams again - RIDICULUS!