But one thing that occurs to me is the fact that the "Expellliarmus" spell is quite significant in the plot, would you like to elaborate Colin?
Well, he uses it to defeat Voldemort at the end but that's mainly because Voldemort was using a wand that 'belonged' to Harry. He also gets told off for using it by Lupin when he is escaping from Privet Drive as it identified him as the real Harry Potter and not one of the decoys.