Studied astrophysics in college, so I've done everything from calc 1-3, diff eq, classical mechanics, every form of algebra, general and special relativity, quantum mechanics and the list goes on.

Looking back, it was a LOT of hard work and TONS of equations that take up an entire piece of paper to write down, but it was a LOT of fun. It also made me feel like I really got my moneys worth out of my college degree, since I was challenged daily and felt like it would never end.