For me, it was an English class that I took this past spring. The goal of the class was simple: to teach us how to write things that people would read. What was discussed really sharpened my appreciation for good writing styles and made me think about the way I wrote, both in an academic setting and elsewhere (maybe even here).
So what about you?
Cultural anthropology and organic chemistry.
Personal typing. Got me up to 20 wpm; I now do 60. That skill made sure I could get a job whenever I needed one.
In college, I took a couple of Sociology classes (I was a Psych major). One that I took was about the social experiences of various minority groups throughout the history of the U.S. (beginning with the Native American tribes that were here when the first explorers arrived).
That may sound goofy, as it has nothing to do with my current profession or my major at the time. But I never liked History at all in school, so I never really learned a lot of stuff. In most History classes I took, the emphasis was on memorizing events, names, and dates, which was not my strong point. However, I became really interested in the same stuff when it was presented from a social aspect.
I don’t know why it was like that, but I am forever grateful. I learned more about our history from my Sociology class than I ever did from any History class.
Marine Biology.
It was only a six week class, plus I got laid twice!
An English essay course I originally took as an elective. It was the final straw that made me decide to change majors.
It probably didn’t do wonders to propel me into a high-paying job, but it for damn sure killed a deep depression I was in at the time. A far better thing, both short and long term.
Statistics and the Behavioral Sciences. Either that or Algebra 301 (the introductory course). The Algebra course was my very first college class, and before that I don’t think I had ever thought quite the way I was required to to pass that course. There is a bit of a story there that I will have to save for a later time.
Statistics and the Behavioral Sciences was the course that tought me to appreciate the difference between good and bad design in experiments, recognize sloppy thinking, and see the hidden agenda in statistics.
Since this is IMHO I will add that Basic Statistics should be a required course in place of one of the currently required Algebra/Trig/Geometry courses.
I was an archaeology major, and the most worthwhile class I took in that regards was Public Archaeology. Taught us all of the regulations that came into play when doing public archaeology, went over NAGPRA, environmental impact surveys, how to secure a permit and all, plus, we got to do hands-on lab work and learned all the major typologies for New England.
But I’d also have to say that Soil Identification and Interpretation course I took ranked up there. Who would’ve thought that a class on dirt could be worthwhile? This one rocked. We learned how to identify wetlands based on the soils found there (very important in public archaeology–wetlands need special permits), and how to interpret soil samples from different types of environments. It’s cool driving down the road and being able to figure out what the land used to be like, based on the strata you see in the soil and rock formations! Plus we got to take field trips all the time and play in the mud.
My senior year in high school I did an independant study with my favorite teacher.
It was hesitantly titled “The study of the creation morality through modern film and literature” or some such.
I have neevr had to think so hard in my life. The teacher is a brilliant, good man. (Who I still adore and have frequent dealings with to my luck) Once or twice a week we would get together and talk about the underlacings of humanity as far as I was able to find them. And then I’d get a new novel or two and a movie to study and come back when I was done. He also acted as an advisor during the rough stuff with my parents. (And my school.)
So I read a whole pile of cool books, watched neat movies, talked about them with the most brilliant, sensitive person I know, and got good advice about life. Probably half my moral code and philosophies came from that ‘class’. (And another 10 percent from his freshman class I was lucky enough to take.)
And people say public schools can’t educate.
It’s a tie between a writing class I took when I first started clooege last fall and a world geography class I’m taking now.
In the writing class, we were asked to reasearch and discuss controversial topics. At the time, I was very closed-minded and naieve (sp?). The class forced me to open my mind up and think about things from another person’s point of view, a skill that that helped me in my writing as well as in life.
In my geography class, we are learning all the countries, their climates, cultures, etc. We barely skim the surface, but it’s basic information that every college educated person should know.
That’s easy. It’s the elective in cognitive science that I took in my third year as an undergrad. That’s where I met my wife for the first time.
High school American history. Not for the subject matter, but because of the teacher’s no-nonsense attitude towards slacker students.
“You don’t want to learn? Fine. Here’s a hall pass, go out and have fun. The rest of us are here to study.”
He couldn’t care less if you diss’d him, or felt it was a waste of your time to be in his class, or whatever. He’d be glad to accomodate the losers and get rid of them just so he’d have a good learning environment for the others. It was no skin off his nose – you were depriving yourself of an education, after all. He gets paid either way.
That was a ballsy attitude that I really admired. I learned a lot in the class, both from the textbook and from his approach to “difficult” students.
Same here. Typing was by FAR the most useful class.
Runner-up:
a writing class that drilled composing speed-essays on random topics.
Most worthless: Fortran. I don’t know why I took this class - I haven’t written a single line of fortran code since, and am sure I never will. (I almost said the LISP class, but I find the concept of LISP useful now and then).
Way back in 1988 during my seinior year of high school, I took Typing because I needed an elective and thought it would be an easy A. I was right about how easy it was, but I am suprised by how handy a skill it has turned out to be.
Damn near everything I took in Cegep and University.
When I decided to answer this question, I was thinking in terms of what the most interesting class I took was. I was going to say it was Philosophy. I really loved this class although I was forced to withdraw before it was over due to personal reasons. I would love to take it again.
Now that I realize that the question is worthwhile class I have to say it was Composition. I learned skills in that class that have helped me in almost every other course I have taken.
It’s been said already (twice) but I’ll kick in for typing as well. Of all the classes I had in high school this is one thing I would not have picked up in college or elsewhere and it has proven more useful by far than any other class I’ve ever taken.
Seventh-grade Geography, first and foremost. A report on the Visigoths ( Yayyyy, Visigoths!!! 
) started a life-long fascination with history. It also got me thinking about the wider world and other cultures. And maps - I loved maps 
. Oddly enough, my teacher was almost ( but certainly not completely ) superfluous to the whole process. It was more the material that seized me, rather than the presentation.
My sophmore year in college and some biology classes I took at that time, were also influential as a group. But not quite as revelatory as that grade-school experience.
An environmental research class I took senior year of high school showed me that if I put my mind to it I could fudge just about anything. The entire course was geared towards one really big project all year and at the end we presented our projects to a panel of professional scientists and college professors taht my teacher knew… Not a single one of them questioned my results and they were all very interested in our project for its thourough research and analysis. Why is this surprising? We made up about half the background and all of the results.
Typing - In high school, it was a 1/2 semester class and I got a B- in it, but it has served me well since then.
Spanish - In high school and college, I work in an area that has a high migrant worker population. The school system I work for has the largest Migrant education program in the state. The spanish has been very useful. Probably the only useful thing I got out of college.