Most Difficult Math Class?

I'm a freshman in college right now, and I'm getting ready to take my Calculus II final here later this week.  I've always been very good at math, but this last semester was by far the most difficult math I've ever taken.  For the first time in my life, I'm actually having to study outside of class, and I'm not certain of at least a high B on this test.

From talking to some of my sophomore buddies and a few of the teachers I'm on good terms with I've heard that Calc II is about the hardest math I will ever take.  Would you guys agree? If not, what was the most difficult math for you?

Calc II is just scratching the surface. The hardest math you will ever take you can't even dream of.

As a good example of some genuinely hard math, go to any university library, and pick up any book that has a yellow cover with a white top to it that says "Graduate texts in mathematics," or whatever the hell they're called. Or if you just want a subject that will kick your ass no matter what you do, try differential forms.