<p>I took a discrete math course, which was pretty straightforward. During it we got a taste of group theory, and it was the single strangest, most abstract concept I have ever been asked to grasp. I’ve never taken an upper division math class, but I’m going to avoid it if at all possible. A man’s got to know his limitations.</p>
<p>What’s purple and commutes? An Abelian Grape.</p>
<p>Advanced Engineering Math @ UCSB for me. Good thing they graded on a curve or I would have needed to transfer to a Cal State to get my degree 
I found linear algebra fun in comparison.</p>
Applied Partial Differential Equations is by far the hardest mathematics course if your minor is in mathematics due to the tediousness of it and large margins for error.
Descriptive Geometry - I took math all the way to DiffEq and linear algebra plus a ton of computer math, stats, probability, and numerical analysis and Descriptive Geometry - essentially the math behind perspective drawing and such, required for Civil Engineering students in the pre-CAD days - was nearly incomprehensible. Not difficult like partial differential equations, just outright incomprehensible.
Sometimes the simplest math is the most powerful though, like that used to calculate that this thread has been open for 7 years, 4 months and 4 days, 2682 days if you prefer. 
Complex Analysis>Partial DEqs>Abstract Algebra>Real Analysis/Calc IV>Linear Algebra>Ordinary DiffEqs>Calc II>Calc III (yeah you read that right)>Calc I
My school requires calc 3 and diff eq. Between the two, most people tend to like one and dislike the other. I personally found diff eq to be the hardest out of the math classes I have taken, but I did not take any math classes beyond the requirements.
This thread was started in 2008. Can’t it just stay dead? Is there REALLY anything new to add?