#10 Hawaiian Hallways
At my high school, we had to wear a button-down shirt and tie to class every day. One of the kids realized that they never specified what kind of button-down shirt it had to be, so he chose to wear Hawaiian shirts every day to class. Technically, it met the dress code so it stuck.
Pretty soon, most of the school started wearing Hawaiian shirts with ties to class. We looked like a bunch of ridiculous Jimmy-Buffet-goes-Mormon types, but it was worth it to spite the system. They changed the rule to ban Hawaiian shirts a week later.
Credit: taylor1288