What the universe can be broken down to at its basest form. One of the most frustrating topics EVER, but when one is able to grasp its complexities, can see the inner workings of nearly EVERYTHING.
Math is friggin' tough, but we all wish we had the ability to see it like John Nash.
Subject that does have real world applications. Important subject to grasp, however most teachers are boring as fuck about teaching it, making most kids resent the subject with a passion. Simply put, if the teacher sucks, you are going to think math sucks.
Any math besides statistics that you learn after seventh grade is just there so they can have some math to teach you. Nobody gives a shit about the quadratic formula. Hell, you won't even use that for engineering! All I can think of using anything above seventh grade for is a math teacher.