1. Neville Longbottom - Harry Potter series
Why Is He An Idiot? Neville begins his wizard's education at Hogwarts as the shy, shuffling, accident-prone little side character. He was the one who provided us, the mockign audience, with a little bit of comic relief on the side. He is the butt of most jokes and injuries, whether being hung from the ceiling by Cornish Pixies or knocked out by a screaming weed, and nobody saw him as anything other than this.
Top Idiotic Moment Poor Neville, all he wants to do is help. After supplying Harry Potter with a weed that gives him gills and webbed feet (Redneck jokes will not be made at this point), the shock of his sudden fishy qualities means Harry doesn't surface. In front of a giant crowd of people (a common theme for our stupid moments), Neville announces "Oh my God, I've killed Harry Potter!", only for the Pot-fish to burst out of the water behind him, sending a cheer through the crowd and a spasm through our blundering subject.
How He Saved the Day Ah, Neville. Young, naive, stupid even. We all saw him and thought "There's not a chance in hell he's going to do anything right." Even when some of the wiser-eyed of us noticed he was beginning to grow up in the wizarding world, nobody could foresee what he would do. When the finale came, it was not Harry, nor was it Hermoine, or Ron, or Fred or George, or any other student. It wasn't Dumbledore, or Snape, or McGonagall or any teacher. It was the one who wasn't going to do anything right. The school is being torn asunder by the destructive Death Eaters in their bid to kill Harry; albeit for a second time (or third, or fourth, I kind of lost count by now. There are at least three). The only way Harry can stop noseless bad guy Voldemort is with somebody destroying the final Horcrux, which just so happens to be the same massive snake Harry unleashes in the beginning of the first film (yeah, I didn't realize that either). When Ron and Hermoine drop the magical mystic sword, it is resident idiot Neville that steps to the plate, saving
everybody and everything from Voldemort's wrath. Harry might be delivering the final blow, but Neville makes the most important hit in the entire film series. Not bad for someone who couldn't use a wand for most of it. If I have missed out any movie idiots (I'm sure I have, there are more than enough of them out there) then let me know in the comments.