By the time I complete my PhD, I'll have spent an entire decade at Stanford (yikes)!
These were my favorite courses :)

ARTSTUDI 141: Plein Air Painting Now
CS 110: Principles of Computer Systems
CS 228: Probabilistic Graphical Models: Principles and Techniques
CS 255: Introduction to Cryptography
CS 265: Randomized Algorithms and Probabilistic Analysis
CS 269O: Introduction to Optimization Theory
ENGR 50M: Introduction to Materials Science
ENGLISH 92: Reading and Writing Poetry
ENGLISH 190: Intermediate Fiction
HUMBIO 162L: The Literature of Psychosis

I also highly recommend the BOSP programs, especially the study abroad program in Oxford, the SETS Global Engineering program, and visiting the Hopkins Marine Station!