AP Calculus (BC) in high school. I had the world's worst teacher. He'd taught the AB curriculum for years. He spent the first four months of the year going over things we'd covered in pre-calc.
On the day before the AP exam, he said, "Well, we didn't get to integrating over a circle, but don't worry, it hasn't been on the test in the past twenty years." Guess what was question 1 of part 2.
In college I had to take multivariable calculus and differential equations, plus a bunch of statistics classes. I HATE STATISTICS. Plus, there was a lot of math worked into my engineering classes. May I never see another z-transform.