Statistics and Econometrics
Recommended for anyone who is fresh new to stats in general. Trust me, it is so far the best basic course one could ever find. I survived my Ph.D. Quantitative Research course hugely thanks to many of Leonard's videos.
Ever wondering what a "model" is; or what "model" to use for which situation? Then, you cannot miss this course from Dr. Katchova at the Ohio State University.